1.
Green fluorescent protein
–
The green fluorescent protein is a protein composed of 238 amino acid residues that exhibits bright green fluorescence when exposed to light in the blue to ultraviolet range. Although many other organisms have similar green fluorescent proteins, GFP traditionally refers to the protein first isolated from the jellyfish Aequorea victoria. The GFP from A. victoria has an excitation peak at a wavelength of 395 nm. Its emission peak is at 509 nm, which is in the green portion of the visible spectrum. The fluorescence quantum yield of GFP is 0.79, the GFP from the sea pansy has a single major excitation peak at 498 nm. In cell and molecular biology, the GFP gene is used as a reporter of expression. GFP can be introduced into animals or other species through transgenic techniques, and maintained in their genome, to date, GFP has been expressed in many species, including bacteria, yeasts, fungi, fish and mammals, including in human cells. Tsien, Osamu Shimomura, and Martin Chalfie were awarded the 2008 Nobel Prize in Chemistry on 10 October 2008 for their discovery and development of the green fluorescent protein. In the 1960s and 1970s, GFP, along with the separate luminescent protein aequorin, was first purified from Aequorea victoria, in A. victoria, GFP fluorescence occurs when aequorin interacts with Ca2+ ions, inducing a blue glow. Some of this luminescent energy is transferred to the GFP, shifting the overall color towards green, however, its utility as a tool for molecular biologists did not begin to be realized until 1992 when Douglas Prasher reported the cloning and nucleotide sequence of wtGFP in Gene. The funding for this project had run out, so Prasher sent cDNA samples to several labs. The lab of Martin Chalfie expressed the coding sequence of wtGFP, with the first few amino acids deleted, in cells of E. coli and C. elegans. Frederick Tsujis lab independently reported the expression of the recombinant protein one month later, remarkably, the GFP molecule folded and was fluorescent at room temperature, without the need for exogenous cofactors specific to the jellyfish. The first reported crystal structure of a GFP was that of the S65T mutant by the Remington group in Science in 1996, one month later, the Phillips group independently reported the wild-type GFP structure in Nature Biotechnology. These crystal structures provided vital background on chromophore formation and neighboring residue interactions, researchers have modified these residues by directed and random mutagenesis to produce the wide variety of GFP derivatives in use today. Due to the potential for widespread usage and the needs of researchers. The first major improvement was a point mutation reported in 1995 in Nature by Roger Tsien. This matched the spectral characteristics of commonly available FITC filter sets, a 37 °C folding efficiency point mutant to this scaffold, yielding enhanced GFP, was discovered in 1995 by the laboratories of Thastrup and Falkow
Green fluorescent protein
–
Structure of the 'Aequorea victoria' green fluorescent protein.
Green fluorescent protein
–
Aequorea victoria
Green fluorescent protein
–
3D reconstruction of confocal image of VEGF-overexpressing neural progenitors (red) and GFP-positive control neural progenitor cells (green) in the rat olfactory bulb. RECA-1-positive blood vessels - blue color.
Green fluorescent protein
–
The diversity of genetic mutations is illustrated by this San Diego beach scene drawn with living bacteria expressing 8 different colors of fluorescent proteins (derived from GFP and dsRed).
2.
Carbonate mineral
–
IMA-CNMNC proposes a new hierarchical scheme. This list uses the Classification of Nickel–Strunz
Carbonate mineral
–
Calcite crystals from the Sweetwater Mine, Viburnum Trend District,
Reynolds County, Missouri - 6.2 × 6 × 3.3 cm
Carbonate mineral
–
Rhodochrosite, Sweet Home Mine, Alma, Colorado - 5.2 × 4.2 × 2.3 cm
Carbonate mineral
–
Smithsonite, Silver Bill Mine, Dragoon Mts,
Cochise County, Arizona - 4.8 × 4.1 × 2.4 cm
Carbonate mineral
–
Dolomite with calcite and chalcopyrite from the Picher Field,
Tri-State district,
Cherokee County, Kansas; 12.0 × 9.7 × 4.3 cm
3.
Chemical formula
–
These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a name, and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulas can fully specify the structure of only the simplest of molecules and chemical substances, the simplest types of chemical formulas are called empirical formulas, which use letters and numbers indicating the numerical proportions of atoms of each type. Molecular formulas indicate the numbers of each type of atom in a molecule. For example, the formula for glucose is CH2O, while its molecular formula is C6H12O6. This is possible if the relevant bonding is easy to show in one dimension, an example is the condensed molecular/chemical formula for ethanol, which is CH3-CH2-OH or CH3CH2OH. For reasons of structural complexity, there is no condensed chemical formula that specifies glucose, chemical formulas may be used in chemical equations to describe chemical reactions and other chemical transformations, such as the dissolving of ionic compounds into solution. A chemical formula identifies each constituent element by its chemical symbol, in empirical formulas, these proportions begin with a key element and then assign numbers of atoms of the other elements in the compound, as ratios to the key element. For molecular compounds, these numbers can all be expressed as whole numbers. For example, the formula of ethanol may be written C2H6O because the molecules of ethanol all contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of compounds, however, cannot be written with entirely whole-number empirical formulas. An example is boron carbide, whose formula of CBn is a variable non-whole number ratio with n ranging from over 4 to more than 6.5. When the chemical compound of the consists of simple molecules. These types of formulas are known as molecular formulas and condensed formulas. A molecular formula enumerates the number of atoms to reflect those in the molecule, so that the formula for glucose is C6H12O6 rather than the glucose empirical formula. However, except for very simple substances, molecular chemical formulas lack needed structural information, for simple molecules, a condensed formula is a type of chemical formula that may fully imply a correct structural formula. For example, ethanol may be represented by the chemical formula CH3CH2OH
Chemical formula
–
Al 2 (SO 4) 3
4.
Crystal system
–
In crystallography, the terms crystal system, crystal family and lattice system each refer to one of several classes of space groups, lattices, point groups or crystals. Informally, two crystals are in the crystal system if they have similar symmetries, though there are many exceptions to this. Space groups and crystals are divided into seven crystal systems according to their point groups, five of the crystal systems are essentially the same as five of the lattice systems, but the hexagonal and trigonal crystal systems differ from the hexagonal and rhombohedral lattice systems. The six crystal families are formed by combining the hexagonal and trigonal crystal systems into one hexagonal family, a lattice system is a class of lattices with the same set of lattice point groups, which are subgroups of the arithmetic crystal classes. The 14 Bravais lattices are grouped into seven lattice systems, triclinic, monoclinic, orthorhombic, tetragonal, rhombohedral, hexagonal, in a crystal system, a set of point groups and their corresponding space groups are assigned to a lattice system. Of the 32 point groups that exist in three dimensions, most are assigned to only one system, in which case both the crystal and lattice systems have the same name. However, five point groups are assigned to two systems, rhombohedral and hexagonal, because both exhibit threefold rotational symmetry. These point groups are assigned to the crystal system. In total there are seven crystal systems, triclinic, monoclinic, orthorhombic, tetragonal, trigonal, hexagonal, a crystal family is determined by lattices and point groups. It is formed by combining crystal systems which have space groups assigned to a lattice system. In three dimensions, the families and systems are identical, except the hexagonal and trigonal crystal systems. In total there are six families, triclinic, monoclinic, orthorhombic, tetragonal, hexagonal. Spaces with less than three dimensions have the number of crystal systems, crystal families and lattice systems. In one-dimensional space, there is one crystal system, in 2D space, there are four crystal systems, oblique, rectangular, square and hexagonal. The relation between three-dimensional crystal families, crystal systems and lattice systems is shown in the table, Note. To avoid confusion of terminology, the term trigonal lattice is not used, if the original structure and inverted structure are identical, then the structure is centrosymmetric. Still, even for non-centrosymmetric case, inverted structure in some cases can be rotated to align with the original structure and this is the case of non-centrosymmetric achiral structure. If the inverted structure cannot be rotated to align with the structure, then the structure is chiral
Crystal system
–
Hexagonal
hanksite crystal, with three-fold c-axis symmetry
Crystal system
–
The
diamond crystal structure belongs to the face-centered
cubic lattice, with a repeated 2-atom pattern.
5.
Monoclinic
–
In crystallography, the monoclinic crystal system is one of the 7 crystal systems. A crystal system is described by three vectors, in the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic system. They form a rectangular prism with a parallelogram as its base, hence two vectors are perpendicular, while the third vector meets the other two at an angle other than 90°. There is only one monoclinic Bravais lattice in two dimensions, the oblique lattice, two monoclinic Bravais lattices exist, the primitive monoclinic and the centered monoclinic lattices. In this axis setting, the primitive and base-centered lattices interchange in centering type, sphenoidal is also monoclinic hemimorphic, Domatic is also monoclinic hemihedral, Prismatic is also monoclinic normal. Crystal structure Hurlbut, Cornelius S. Klein, Cornelis, hahn, Theo, ed. International Tables for Crystallography, Volume A, Space Group Symmetry
Monoclinic
–
An example of the monoclinic crystals,
orthoclase
6.
Crystal class
–
For a periodic crystal, the group must also be consistent with maintenance of the three-dimensional translational symmetry that defines crystallinity. The macroscopic properties of a crystal would look exactly the same before, in the classification of crystals, each point group is also known as a crystal class. There are infinitely many three-dimensional point groups, however, the crystallographic restriction of the infinite families of general point groups results in there being only 32 crystallographic point groups. These 32 point groups are one-and-the same as the 32 types of morphological crystalline symmetries derived in 1830 by Johann Friedrich Christian Hessel from a consideration of observed crystal forms, the point groups are denoted by their component symmetries. There are a few standard notations used by crystallographers, mineralogists, for the correspondence of the two systems below, see crystal system. In Schoenflies notation, point groups are denoted by a symbol with a subscript. The symbols used in crystallography mean the following, Cn indicates that the group has a rotation axis. Cnh is Cn with the addition of a plane perpendicular to the axis of rotation. Cnv is Cn with the addition of n mirror planes parallel to the axis of rotation, s2n denotes a group that contains only a 2n-fold rotation-reflection axis. Dn indicates that the group has a rotation axis plus n twofold axes perpendicular to that axis. Dnh has, in addition, a plane perpendicular to the n-fold axis. Dnd has, in addition to the elements of Dn, mirror planes parallel to the n-fold axis, the letter T indicates that the group has the symmetry of a tetrahedron. Td includes improper rotation operations, T excludes improper rotation operations, the letter O indicates that the group has the symmetry of an octahedron, with or without improper operations. Due to the crystallographic restriction theorem, n =1,2,3,4, d4d and D6d are actually forbidden because they contain improper rotations with n=8 and 12 respectively. The 27 point groups in the table plus T, Td, Th, O, an abbreviated form of the Hermann–Mauguin notation commonly used for space groups also serves to describe crystallographic point groups. Group names are Molecular symmetry Point group Space group Point groups in three dimensions Crystal system Point-group symbols in International Tables for Crystallography,12.1, pp. 818-820 Names and symbols of the 32 crystal classes in International Tables for Crystallography. 10.1, p.794 Pictorial overview of the 32 groups Point Groups - Flow Chart Inorganic Chemistry Group Theory Practice Problems
Crystal class
–
Class
7.
H-M symbol
–
In geometry, Hermann–Mauguin notation is used to represent the symmetry elements in point groups, plane groups and space groups. It is named after the German crystallographer Carl Hermann and the French mineralogist Charles-Victor Mauguin and this notation is sometimes called international notation, because it was adopted as standard by the International Tables For Crystallography since their first edition in 1935. Rotation axes are denoted by a number n —1,2,3,4,5,6,7,8, for improper rotations, Hermann–Mauguin symbols show rotoinversion axes, unlike Schoenflies and Shubnikov notations, where the preference is given to rotation-reflection axes. The rotoinversion axes are represented by the number with a macron. The symbol for a plane is m. The direction of the plane is defined as the direction of perpendicular to the face. Hermann–Mauguin symbols show symmetrically non-equivalent axes and planes, the direction of a symmetry element is represented by its position in the Hermann–Mauguin symbol. If a rotation axis n and a mirror plane m have the same direction, if two or more axes have the same direction, the axis with higher symmetry is shown. Higher symmetry means that the axis generates a pattern with more points, for example, rotation axes 3,4,5,6,7,8 generate 3-, 4-, 5-, 6-, 7-, 8-point patterns, respectively. Improper rotation axes 3,4,5,6,7,8 generate 6-, 4-, 10-, 6-, 14-, 8-point patterns, if both, the rotation and rotoinversion axes satisfy the previous rule, the rotation axis should be chosen. For example, 3/m combination is equivalent to 6, since 6 generates 6 points, and 3 generates only 3,6 should be written instead of 3/m. Analogously, in the case when both 3 and 3 axes are present,3 should be written, however we write 4/m, not 4/m, because both 4 and 4 generate four points. Finally, the Hermann–Mauguin symbol depends on the type of the group and these groups may contain only two-fold axes, mirror planes, and inversion center. These are the point groups 1 and 1,2, m, and 2/m, and 222, 2/m2/m2/m. If the symbol contains three positions, then they denote symmetry elements in the x, y, z direction, First position — primary direction — z direction, assigned to the higher-order axis. Second position — symmetrically equivalent secondary directions, which are perpendicular to the z-axis and these can be 2, m, or 2/m. Third position — symmetrically equivalent tertiary directions, passing between secondary directions and these can be 2, m, or 2/m. These are the crystallographic groups 3,32, 3m,3, and 32/m,4,422, 4mm,4, 42m, 4/m, and 4/m2/m2/m, and 6,622, 6mm,6, 6m2, 6/m, and 6/m2/m2/m
H-M symbol
–
Contents
8.
Space group
–
In mathematics, physics and chemistry, a space group is the symmetry group of a configuration in space, usually in three dimensions. In three dimensions, there are 219 distinct types, or 230 if chiral copies are considered distinct, Space groups are also studied in dimensions other than 3 where they are sometimes called Bieberbach groups, and are discrete cocompact groups of isometries of an oriented Euclidean space. In crystallography, space groups are called the crystallographic or Fedorov groups. A definitive source regarding 3-dimensional space groups is the International Tables for Crystallography, in 1879 Leonhard Sohncke listed the 65 space groups whose elements preserve the orientation. More accurately, he listed 66 groups, but Fedorov and Schönflies both noticed that two of them were really the same, the space groups in 3 dimensions were first enumerated by Fedorov, and shortly afterwards were independently enumerated by Schönflies. The correct list of 230 space groups was found by 1892 during correspondence between Fedorov and Schönflies, burckhardt describes the history of the discovery of the space groups in detail. The space groups in three dimensions are made from combinations of the 32 crystallographic point groups with the 14 Bravais lattices, the combination of all these symmetry operations results in a total of 230 different space groups describing all possible crystal symmetries. The elements of the space group fixing a point of space are rotations, reflections, the identity element, the translations form a normal abelian subgroup of rank 3, called the Bravais lattice. There are 14 possible types of Bravais lattice, the quotient of the space group by the Bravais lattice is a finite group which is one of the 32 possible point groups. Translation is defined as the moves from one point to another point. A glide plane is a reflection in a plane, followed by a parallel with that plane. This is noted by a, b or c, depending on which axis the glide is along. There is also the n glide, which is a glide along the half of a diagonal of a face, and the d glide, the latter is called the diamond glide plane as it features in the diamond structure. In 17 space groups, due to the centering of the cell, the glides occur in two directions simultaneously, i. e. the same glide plane can be called b or c, a or b. For example, group Abm2 could be also called Acm2, group Ccca could be called Cccb, in 1992, it was suggested to use symbol e for such planes. The symbols for five groups have been modified, A screw axis is a rotation about an axis. These are noted by a number, n, to describe the degree of rotation, the degree of translation is then added as a subscript showing how far along the axis the translation is, as a portion of the parallel lattice vector. So,21 is a rotation followed by a translation of 1/2 of the lattice vector
Space group
–
The space group of hexagonal H 2 O ice is P6 3 / mmc. The first m indicates the mirror plane perpendicular to the c-axis (a), the second m indicates the mirror planes parallel to the c-axis (b) and the c indicates the glide planes (b) and (c). The black boxes outline the unit cell.
9.
Crystal structure
–
In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the nature of the constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter. The smallest group of particles in the material that constitutes the pattern is the unit cell of the structure. The unit cell completely defines the symmetry and structure of the crystal lattice. The repeating patterns are said to be located at the points of the Bravais lattice, the lengths of the principal axes, or edges, of the unit cell and the angles between them are the lattice constants, also called lattice parameters. The symmetry properties of the crystal are described by the concept of space groups, all possible symmetric arrangements of particles in three-dimensional space may be described by the 230 space groups. The crystal structure and symmetry play a role in determining many physical properties, such as cleavage, electronic band structure. The crystal structure of a material can be described in terms of its unit cell, the unit cell is a box containing one or more atoms arranged in three dimensions. The unit cells stacked in three-dimensional space describe the arrangement of atoms of the crystal. Commonly, atomic positions are represented in terms of fractional coordinates, the atom positions within the unit cell can be calculated through application of symmetry operations to the asymmetric unit. The asymmetric unit refers to the smallest possible occupation of space within the unit cell and this does not, however imply that the entirety of the asymmetric unit must lie within the boundaries of the unit cell. Symmetric transformations of atom positions are calculated from the group of the crystal structure. Vectors and planes in a lattice are described by the three-value Miller index notation. It uses the indices ℓ, m, and n as directional parameters, which are separated by 90°, by definition, the syntax denotes a plane that intercepts the three points a1/ℓ, a2/m, and a3/n, or some multiple thereof. That is, the Miller indices are proportional to the inverses of the intercepts of the plane with the unit cell, if one or more of the indices is zero, it means that the planes do not intersect that axis. A plane containing a coordinate axis is translated so that it no longer contains that axis before its Miller indices are determined, the Miller indices for a plane are integers with no common factors. Negative indices are indicated with horizontal bars, as in, in an orthogonal coordinate system for a cubic cell, the Miller indices of a plane are the Cartesian components of a vector normal to the plane. Likewise, the planes are geometric planes linking nodes
Crystal structure
–
Quartz is one of the several thermodynamically stable
crystalline forms of
silica, SiO 2. The most important forms of silica include:
α-quartz,
β-quartz,
tridymite,
cristobalite,
coesite, and
stishovite.
Crystal structure
10.
Crystal habit
–
In mineralogy, crystal habit is the characteristic external shape of an individual crystal or crystal group. A single crystals habit is a description of its shape and its crystallographic forms. Recognizing the habit may help in identifying a mineral, when the faces are well-developed due to uncrowded growth a crystal is called euhedral, one with partially developed faces is subhedral, and one with undeveloped crystal faces is called anhedral. The long axis of a quartz crystal typically has a six-sided prismatic habit with parallel opposite faces. Aggregates can be formed of individual crystals with euhedral to anhedral grains, the arrangement of crystals within the aggregate can be characteristic of certain minerals. For example, minerals used for asbestos insulation often grow in a fibrous habit, the terms used by mineralogists to report crystal habits describe the typical appearance of an ideal mineral. Recognizing the habit can aid in identification as some habits are characteristic, most minerals, however, do not display ideal habits due to conditions during crystallization. Minerals belonging to the crystal system do not necessarily exhibit the same habit. Some habits of a mineral are unique to its variety and locality, For example, while most sapphires form elongate barrel-shaped crystals, ordinarily, the latter habit is seen only in ruby. Sapphire and ruby are both varieties of the mineral, corundum. Some minerals may replace other existing minerals while preserving the originals habit, a classic example is tigers eye quartz, crocidolite asbestos replaced by silica. While quartz typically forms prismatic crystals, in tigers eye the original fibrous habit of crocidolite is preserved, the names of crystal habits are derived from, Predominant crystal faces. Abnormal grain growth Grain growth Crystallization
Crystal habit
–
Pyrite sun (or dollar) in laminated shale matrix. Between tightly spaced layers of shale, the aggregate was forced to grow in a laterally compressed, radiating manner. Under normal conditions, pyrite would form cubes or pyritohedrons.
Crystal habit
–
Goethite replacing
pyrite cubes
Crystal habit
–
Acicular
Crystal habit
–
Amygdaloidal
11.
Crystal twinning
–
Crystal twinning occurs when two separate crystals share some of the same crystal lattice points in a symmetrical manner. The result is an intergrowth of two separate crystals in a variety of specific configurations, a twin boundary or composition surface separates the two crystals. Crystallographers classify twinned crystals by a number of twin laws and these twin laws are specific to the crystal system. The type of twinning can be a tool in mineral identification. Twinning can often be a problem in X-ray crystallography, as a crystal does not produce a simple diffraction pattern. Simple twinned crystals may be contact twins or penetration twins, contact twins share a single composition surface often appearing as mirror images across the boundary. Plagioclase, quartz, gypsum, and spinel often exhibit contact twinning, merohedral twinning occurs when the lattices of the contact twins superimpose in three dimensions, such as by relative rotation of one twin from the other. In penetration twins the individual crystals have the appearance of passing through each other in a symmetrical manner, orthoclase, staurolite, pyrite, and fluorite often show penetration twinning. If several twin crystal parts are aligned by the same twin law they are referred to as multiple or repeated twins, if these multiple twins are aligned in parallel they are called polysynthetic twins. When the multiple twins are not parallel they are cyclic twins, albite, calcite, and pyrite often show polysynthetic twinning. Closely spaced polysynthetic twinning is often observed as striations or fine lines on the crystal face. Rutile, aragonite, cerussite, and chrysoberyl often exhibit cyclic twinning, 2-normal twin, -when the twin plane and compositional plane lies noramally. 3-complex twin, -combination of parallel twinning and normal twinning on one compositional plane, there are three modes of formation of twinned crystals. Growth twins are the result of an interruption or change in the lattice during formation or growth due to a possible deformation from a larger substituting ion, deformation or gliding twins are the result of stress on the crystal after the crystal has formed. If a FCC metal like aluminum experiences extreme stresses, it will experience twinning as seen in the case of explosions, deformation twinning is a common result of regional metamorphism. Crystals that grow adjacent to each other may be aligned to resemble twinning and this parallel growth simply reduces system energy and is not twinning. Twin boundaries occur when two crystals of the same type intergrow, so only a slight misorientation exists between them. It is a highly symmetrical interface, often with one crystal the mirror image of the other, also and this is also a much lower-energy interface than the grain boundaries that form when crystals of arbitrary orientation grow together
Crystal twinning
–
Quartz - Japan twin
Crystal twinning
–
Diagram of twinned crystals of
Albite. On the more perfect cleavage, which is parallel to the
basal plane (P), is a system of fine striations, parallel to the second cleavage (M).
Crystal twinning
–
Twinned pyrite crystal group
Crystal twinning
–
Galvanized surface with macroscopic crystalline features. Twin boundaries are visible as striations within each
crystallite, most prominently in the bottom-left and top-right.
12.
Cleavage (crystal)
–
Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite crystallographic structural planes. Cleavage forms parallel to planes, Basal or pinacoidal cleavage occurs when there is only one cleavage plane. Mica also has basal cleavage, this is why mica can be peeled into thin sheets, cubic cleavage occurs on when there are three cleavage planes intersecting at 90 degrees. Halite has cubic cleavage, and therefore, when halite crystals are broken, octahedral cleavage occurs when there are four cleavage planes in a crystal. Octahedral cleavage is common for semiconductors, rhombohedral cleavage occurs when there are three cleavage planes intersecting at angles that are not 90 degrees. Prismatic cleavage occurs when there are two planes in a crystal. Dodecahedral cleavage occurs when there are six cleavage planes in a crystal, crystal parting occurs when minerals break along planes of structural weakness due to external stress or along twin composition planes. Parting breaks are very similar in appearance to cleavage, but only due to stress. Examples include magnetite which shows octahedral parting, the parting of corundum. Cleavage is a property traditionally used in mineral identification, both in hand specimen and microscopic examination of rock and mineral studies. As an example, the angles between the cleavage planes for the pyroxenes and the amphiboles are diagnostic. Crystal cleavage is of importance in the electronics industry and in the cutting of gemstones. Precious stones are generally cleaved by impact, as in diamond cutting, synthetic single crystals of semiconductor materials are generally sold as thin wafers which are much easier to cleave. Elemental semiconductors are diamond cubic, a group for which octahedral cleavage is observed. This means that some orientations of wafer allow near-perfect rectangles to be cleaved, most other commercial semiconductors can be made in the related zinc blende structure, with similar cleavage planes. Cleavage Mineral galleries, Mineral properties – Cleavage
Cleavage (crystal)
–
Green
fluorite with prominent cleavage.
Cleavage (crystal)
–
Biotite with basal cleavage.
13.
Fracture (mineralogy)
–
In the field of mineralogy, fracture is the texture and shape of a rocks surface formed when a mineral is fractured. Minerals often have a highly distinctive fracture, making it a feature used in their identification. Fracture differs from cleavage in that the latter involves clean splitting along the planes of the minerals crystal structure. All minerals exhibit fracture, but when very strong cleavage is present, conchoidal fracture breakage that resembles the concentric ripples of a mussel shell. It often occurs in amorphous or fine-grained minerals such as flint, opal or obsidian, subconchoidal fracture is similar to conchoidal fracture, but with less significant curvature. Earthy fracture is reminiscent of freshly broken soil and it is frequently seen in relatively soft, loosely bound minerals, such as limonite, kaolinite and aluminite. Hackly fracture is jagged, sharp and not even and it occurs when metals are torn, and so is often encountered in native metals such as copper and silver. Splintery fracture comprises sharp elongated points and it is particularly seen in fibrous minerals such as chrysotile, but may also occur in non-fibrous minerals such as kyanite. Uneven fracture is a surface or one with random irregularities. It occurs in a range of minerals including arsenopyrite, pyrite and magnetite. Rudolf Duda and Lubos Rejl, Minerals of the World http, //www. galleries. com/minerals/property/fracture. htm
Fracture (mineralogy)
–
Obsidian
Fracture (mineralogy)
–
Limonite
Fracture (mineralogy)
–
Native copper
Fracture (mineralogy)
–
Chrysotile
14.
Mohs scale of mineral hardness
–
The Mohs scale of mineral hardness is a qualitative ordinal scale characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. Created in 1812 by German geologist and mineralogist Friedrich Mohs, it is one of several definitions of hardness in materials science, while greatly facilitating the identification of minerals in the field, the Mohs scale does not show how well hard materials perform in an industrial setting. Despite its lack of precision, the Mohs scale is highly relevant for field geologists, the Mohs scale hardness of minerals can be commonly found in reference sheets. Reference materials may be expected to have a uniform Mohs hardness, the Mohs scale of mineral hardness is based on the ability of one natural sample of mineral to scratch another mineral visibly. The samples of matter used by Mohs are all different minerals, Minerals are pure substances found in nature. Rocks are made up of one or more minerals, as the hardest known naturally occurring substance when the scale was designed, diamonds are at the top of the scale. The hardness of a material is measured against the scale by finding the hardest material that the material can scratch. For example, if material is scratched by apatite but not by fluorite. Scratching a material for the purposes of the Mohs scale means creating non-elastic dislocations visible to the naked eye, frequently, materials that are lower on the Mohs scale can create microscopic, non-elastic dislocations on materials that have a higher Mohs number. The Mohs scale is an ordinal scale. For example, corundum is twice as hard as topaz, the table below shows the comparison with the absolute hardness measured by a sclerometer, with pictorial examples. On the Mohs scale, a streak plate has a hardness of 7.0, using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale. The table below incorporates additional substances that may fall between levels, Comparison between Hardness and Hardness, Mohs hardness of elements is taken from G. V, samsonov in Handbook of the physicochemical properties of the elements, IFI-Plenum, New York, USA,1968. The Hardness of Minerals and Rocks
Mohs scale of mineral hardness
Mohs scale of mineral hardness
Mohs scale of mineral hardness
Mohs scale of mineral hardness
15.
Lustre (mineralogy)
–
Lustre or luster is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the latin lux, meaning light, a range of terms are used to describe lustre, such as earthy, metallic, greasy, and silky. Similarly, the term refers to a glassy lustre. A list of terms is given below. Lustre varies over a continuum, and so there are no rigid boundaries between the different types of lustre. The terms are frequently combined to describe types of lustre. Some minerals exhibit unusual optical phenomena, such as asterism or chatoyancy, a list of such phenomena is given below. Adamantine minerals possess a superlative lustre, which is most notably seen in diamond, such minerals are transparent or translucent, and have a high refractive index. Minerals with an adamantine lustre are uncommon, with examples being cerussite. Minerals with a degree of lustre are referred to as subadamantine, with some examples being garnet. Dull minerals exhibit little to no lustre, due to coarse granulations which scatter light in all directions, a distinction is sometimes drawn between dull minerals and earthy minerals, with the latter being coarser, and having even less lustre. Greasy minerals resemble fat or grease, a greasy lustre often occurs in minerals containing a great abundance of microscopic inclusions, with examples including opal and cordierite. Many minerals with a greasy lustre also feel greasy to the touch, metallic minerals have the lustre of polished metal, and with ideal surfaces will work as a reflective surface. Examples include galena, pyrite and magnetite, pearly minerals consist of thin transparent co-planar sheets. Light reflecting from these layers give them a lustre reminiscent of pearls, such minerals possess perfect cleavage, with examples including muscovite and stilbite. Resinous minerals have the appearance of resin, chewing gum or plastic, a principal example is amber, which is a form of fossilized resin. Silky minerals have an arrangement of extremely fine fibres, giving them a lustre reminiscent of silk. Examples include asbestos, ulexite and the satin spar variety of gypsum, a fibrous lustre is similar, but has a coarser texture
Lustre (mineralogy)
–
Cut diamonds.
Lustre (mineralogy)
–
Kaolinite
Lustre (mineralogy)
–
Moss
opal
Lustre (mineralogy)
–
Pyrite
16.
Streak (mineralogy)
–
The streak of a mineral is the color of the powder produced when it is dragged across an un-weathered surface. If no streak seems to be made, the streak is said to be white or colorless. Streak is particularly important as a diagnostic for opaque and colored materials and it is less useful for silicate minerals, most of which have a white streak or are too hard to powder easily. The apparent color of a mineral can vary widely because of impurities or a disturbed macroscopic crystal structure. Small amounts of an impurity that strongly absorbs a particular wavelength can radically change the wavelengths of light that are reflected by the specimen, and thus change the apparent color. However, when the specimen is dragged to produce a streak, it is broken into randomly oriented microscopic crystals, the surface across which the mineral is dragged is called a streak plate, and is generally made of unglazed porcelain tile. In the absence of a plate, the unglazed underside of a porcelain bowl or vase or the back of a glazed tile will work. Sometimes a streak is more easily or accurately described by comparing it with the streak made by another streak plate. Because the trail left behind results from the mineral being crushed into powder, in case of harder minerals, the color of the powder can be determined by filing or crushing with a hammer a small sample, which is then usually rubbed on a streak plate. Most minerals that are harder have a white streak. Some minerals leave a similar to their natural color, such as cinnabar. Other minerals leave surprising colors, such as fluorite, which always has a streak, although it can appear in purple, blue, yellow. Hematite, which is black in appearance, leaves a red streak which accounts for its name, galena, which can be similar in appearance to hematite, is easily distinguished by its gray streak. Hamilton, W. R. Cambridge Guide to Minerals, Rocks, the Encyclopedia of Gemstones and Minerals. New York, Facts on File. p.251, physical Characteristics of Minerals, at Introduction to Mineralogy by Andrea Bangert What is Streak
Streak (mineralogy)
–
Streak plates with
pyrite (left) and
rhodochrosite (right)
17.
Transparency and translucency
–
In the field of optics, transparency is the physical property of allowing light to pass through the material without being scattered. On a macroscopic scale, the photons can be said to follow Snells Law, in other words, a translucent medium allows the transport of light while a transparent medium not only allows the transport of light but allows for image formation. The opposite property of translucency is opacity, transparent materials appear clear, with the overall appearance of one color, or any combination leading up to a brilliant spectrum of every color. When light encounters a material, it can interact with it in different ways. These interactions depend on the wavelength of the light and the nature of the material, photons interact with an object by some combination of reflection, absorption and transmission. Some materials, such as glass and clean water, transmit much of the light that falls on them and reflect little of it. Many liquids and aqueous solutions are highly transparent, absence of structural defects and molecular structure of most liquids are mostly responsible for excellent optical transmission. Materials which do not transmit light are called opaque, many such substances have a chemical composition which includes what are referred to as absorption centers. Many substances are selective in their absorption of light frequencies. They absorb certain portions of the spectrum while reflecting others. The frequencies of the spectrum which are not absorbed are either reflected or transmitted for our physical observation and this is what gives rise to color. The attenuation of light of all frequencies and wavelengths is due to the mechanisms of absorption. Transparency can provide almost perfect camouflage for animals able to achieve it and this is easier in dimly-lit or turbid seawater than in good illumination. Many marine animals such as jellyfish are highly transparent, at the atomic or molecular level, physical absorption in the infrared portion of the spectrum depends on the frequencies of atomic or molecular vibrations or chemical bonds, and on selection rules. Nitrogen and oxygen are not greenhouse gases because there is no absorption because there is no molecular dipole moment. With regard to the scattering of light, the most critical factor is the scale of any or all of these structural features relative to the wavelength of the light being scattered. Primary material considerations include, Crystalline structure, whether or not the atoms or molecules exhibit the long-range order evidenced in crystalline solids, glassy structure, scattering centers include fluctuations in density or composition. Microstructure, scattering centers include internal surfaces such as boundaries, crystallographic defects
Transparency and translucency
–
Dichroic filters are created using optically transparent materials.
Transparency and translucency
–
Translucency of a material being used to highlight the structure of a photographic subject
Transparency and translucency
–
Meiningen Catholic Church, 20th century glass
Transparency and translucency
–
A laser beam bouncing down an
acrylic rod, illustrating the total internal reflection of light in a multimode optical fiber
18.
Specific gravity
–
This page is about the measurement using water as a reference. For a general use of gravity, see relative density. See intensive property for the property implied by specific, Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is always water at its densest for liquids. Nonetheless, the temperature and pressure must be specified for both the sample and the reference, pressure is nearly always 1 atm. Temperatures for both sample and reference vary from industry to industry, in British beer brewing, the practice for specific gravity as specified above is to multiply it by 1000. Being a ratio of densities, specific gravity is a dimensionless quantity, Specific gravity varies with temperature and pressure, reference and sample must be compared at the same temperature and pressure or be corrected to a standard reference temperature and pressure. Substances with a gravity of 1 are neutrally buoyant in water. Those with SG greater than 1 are denser than water and will, disregarding surface tension effects and those with an SG less than 1 are less dense than water and will float on it. In scientific work, the relationship of mass to volume is expressed directly in terms of the density of the substance under study. It is in industry where specific gravity finds wide application, often for historical reasons. True specific gravity can be expressed mathematically as, S G true = ρ sample ρ H2 O where ρ sample is the density of the sample, the density of water varies with temperature and pressure as does the density of the sample. So it is necessary to specify the temperatures and pressures at which the densities or weights were determined and it is nearly always the case that measurements are made at 1 nominal atmosphere. For true specific gravity calculations, air pressure must be considered, temperatures are specified by the notation with T s representing the temperature at which the samples density was determined and T r the temperature at which the reference density is specified. For example, SG would be understood to mean that the density of the sample was determined at 20°C and of the water at 4°C. Taking into account different sample and reference temperatures, we note that, while S G H2 O =1.000000, it is also the case that S G H2 O =0.998203 /0.999840 =0.998363. Here, temperature is being specified using the current ITS-90 scale, on the previous IPTS-68 scale, the densities at 20 °C and 4 °C are 0.9982071 and 0.9999720 respectively, resulting in an SG value for water of 0.9982343. For example, in the industry, the Plato table lists sucrose concentration by weight against true SG
Specific gravity
–
Testing specific gravity of fuel.
19.
Refractive index
–
In optics, the refractive index or index of refraction n of a material is a dimensionless number that describes how light propagates through that medium. It is defined as n = c v, where c is the speed of light in vacuum, for example, the refractive index of water is 1.333, meaning that light travels 1.333 times faster in a vacuum than it does in water. The refractive index determines how light is bent, or refracted. The refractive indices also determine the amount of light that is reflected when reaching the interface, as well as the angle for total internal reflection. This implies that vacuum has a index of 1. The refractive index varies with the wavelength of light and this is called dispersion and causes the splitting of white light into its constituent colors in prisms and rainbows, and chromatic aberration in lenses. Light propagation in absorbing materials can be described using a refractive index. The imaginary part then handles the attenuation, while the real part accounts for refraction, the concept of refractive index is widely used within the full electromagnetic spectrum, from X-rays to radio waves. It can also be used with wave phenomena such as sound, in this case the speed of sound is used instead of that of light and a reference medium other than vacuum must be chosen. Thomas Young was presumably the person who first used, and invented, at the same time he changed this value of refractive power into a single number, instead of the traditional ratio of two numbers. The ratio had the disadvantage of different appearances, newton, who called it the proportion of the sines of incidence and refraction, wrote it as a ratio of two numbers, like 529 to 396. Hauksbee, who called it the ratio of refraction, wrote it as a ratio with a fixed numerator, hutton wrote it as a ratio with a fixed denominator, like 1.3358 to 1. Young did not use a symbol for the index of refraction, in the next years, others started using different symbols, n, m, and µ. For visible light most transparent media have refractive indices between 1 and 2, a few examples are given in the adjacent table. These values are measured at the yellow doublet D-line of sodium, with a wavelength of 589 nanometers, gases at atmospheric pressure have refractive indices close to 1 because of their low density. Almost all solids and liquids have refractive indices above 1.3, aerogel is a very low density solid that can be produced with refractive index in the range from 1.002 to 1.265. Moissanite lies at the end of the range with a refractive index as high as 2.65. Most plastics have refractive indices in the range from 1.3 to 1.7, for infrared light refractive indices can be considerably higher
Refractive index
–
Thomas Young coined the term index of refraction.
Refractive index
–
A
ray of light being
refracted in a plastic block.
Refractive index
–
Diamonds have a very high refractive index of 2.42.
Refractive index
–
A
split-ring resonator array arranged to produce a negative index of refraction for
microwaves.
20.
Birefringence
–
Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are said to be birefringent, the birefringence is often quantified as the maximum difference between refractive indices exhibited by the material. Crystals with non-cubic crystal structures are often birefringent, as are plastics under mechanical stress and this effect was first described by the Danish scientist Rasmus Bartholin in 1669, who observed it in calcite, a crystal having one of the strongest birefringences. A mathematical description of wave propagation in a birefringent medium is presented below, following is a qualitative explanation of the phenomenon. Thus rotating the material around this axis does not change its optical behavior and this special direction is known as the optic axis of the material. Light whose polarization is perpendicular to the axis is governed by a refractive index no. Light whose polarization is in the direction of the optic axis sees an optical index ne, for any ray direction there is a linear polarization direction perpendicular to the optic axis, and this is called an ordinary ray. The magnitude of the difference is quantified by the birefringence, Δ n = n e − n o, the propagation of the ordinary ray is simply described by no as if there were no birefringence involved. However the extraordinary ray, as its name suggests, propagates unlike any wave in an optical material. Its refraction at a surface can be using the effective refractive index. However it is in fact an inhomogeneous wave whose power flow is not exactly in the direction of the wave vector and this causes an additional shift in that beam, even when launched at normal incidence, as is popularly observed using a crystal of calcite as photographed above. Rotating the calcite crystal will cause one of the two images, that of the ray, to rotate slightly around that of the ordinary ray. When the light propagates either along or orthogonal to the optic axis, in the first case, both polarizations see the same effective refractive index, so there is no extraordinary ray. In the second case the extraordinary ray propagates at a different phase velocity but is not an inhomogeneous wave, for instance, a quarter-wave plate is commonly used to create circular polarization from a linearly polarized source. The case of so-called biaxial crystals is substantially more complex and these are characterized by three refractive indices corresponding to three principal axes of the crystal. For most ray directions, both polarizations would be classified as extraordinary rays but with different effective refractive indices, being extraordinary waves, however, the direction of power flow is not identical to the direction of the wave vector in either case. The two refractive indices can be determined using the index ellipsoids for given directions of the polarization, note that for biaxial crystals the index ellipsoid will not be an ellipsoid of revolution but is described by three unequal principle refractive indices nα, nβ and nγ. Thus there is no axis around which a rotation leaves the optical properties invariant, for this reason, birefringent materials with three distinct refractive indices are called biaxial
Birefringence
–
A
calcite crystal laid upon a graph paper with blue lines showing the double refraction
Birefringence
–
Incoming light in the parallel (s) polarization sees a different effective
index of refraction than light in the perpendicular (p) polarization, and is thus
refracted at a different angle.
Birefringence
–
Urate crystals, with the crystals with their long axis seen as horizontal in this view being parallel to that of a red compensator filter. These appear as yellow, and are thereby of negative birefringence.
Birefringence
–
Color pattern of a plastic box with "frozen in"
mechanical stress placed between two crossed
polarizers.
21.
Pleochroism
–
Pleochroism is an optical phenomenon in which a substance appears to be different colors when observed at different angles, especially with polarized light. Anisotropic crystals will have properties that vary with the direction of light. The polarization of light determines the direction of the electric field and these kinds of crystals have one or two optical axes. If absorption of light varies with the relative to the optical axis in a crystal then pleochroism results. Anisotropic crystals have double refraction of light where light of different polarizations is bent different amounts by the crystal, the components of a divided light beam follow different paths within the mineral and travel at different speeds. When the mineral is observed at some angle, light following some combination of paths and polarizations will be present, at another angle, the light passing through the crystal will be composed of another combination of light paths and polarizations, each with their own color. The light passing through the mineral will therefore have different colors when it is viewed from different angles, tetragonal, trigonal and hexagonal minerals can only show two colors and are called dichroic. Orthorhombic, monoclinic and triclinic crystals can show three and are trichroic, for example, hypersthene, with two optical axes, can have red, yellow or blue appearance when oriented in three different ways in three-dimensional space. Tourmaline is notable for exhibiting strong pleochroism, gems are sometimes cut and set either to display pleochroism or to hide it, depending on the colors and their attractiveness. The pleochroic colours are at their maximum when light is polarized parallel with a crystallographic axis, the axes are designated X, Y and Z. These axes can be determined from the appearance of a crystal in an interference pattern. Where there are two axes, the acute bisection of the axes gives Z for positive minerals and X for negative minerals. Perpendicular to these is the Y axis, the colour is measured with the polarization parallel to each direction. An absorption formula records the amount of parallel to each axis in the form of X < Y < Z with the left most having the least absorption. Minerals that are very similar often have very different pleochroic color schemes. In such cases, a section of the mineral is used and examined under polarized transmitted light with a petrographic microscope. Another device using this property to identify minerals is the dichroscope
Pleochroism
–
Cordierite
Pleochroism
–
Tourmaline
22.
Dispersion (optics)
–
In optics, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency. Media having this property may be termed dispersive media. Sometimes the term chromatic dispersion is used for specificity, the most familiar example of dispersion is probably a rainbow, in which dispersion causes the spatial separation of a white light into components of different wavelengths. Most often, chromatic dispersion refers to material dispersion, that is. However, in a waveguide there is also the phenomenon of waveguide dispersion, more generally, waveguide dispersion can occur for waves propagating through any inhomogeneous structure, whether or not the waves are confined to some region. In a waveguide, both types of dispersion will generally be present, although they are not strictly additive, for example, in fiber optics the material and waveguide dispersion can effectively cancel each other out to produce a zero-dispersion wavelength, important for fast fiber-optic communication. Material dispersion can be a desirable or undesirable effect in optical applications, the dispersion of light by glass prisms is used to construct spectrometers and spectroradiometers. Holographic gratings are used, as they allow more accurate discrimination of wavelengths. However, in lenses, dispersion causes chromatic aberration, an effect that may degrade images in microscopes, telescopes. The phase velocity, v, of a wave in a uniform medium is given by v = c n where c is the speed of light in a vacuum. In general, the index is some function of the frequency f of the light, thus n = n, or alternatively. The wavelength dependence of a refractive index is usually quantified by its Abbe number or its coefficients in an empirical formula such as the Cauchy or Sellmeier equations. In particular, for materials, the susceptibility χ that appears in the Kramers–Kronig relations is the electric susceptibility χe = n2 −1. The most commonly seen consequence of dispersion in optics is the separation of light into a color spectrum by a prism. From Snells law it can be seen that the angle of refraction of light in a prism depends on the index of the prism material. For visible light, refraction indices n of most transparent materials decrease with increasing wavelength λ,1 < n < n < n, or alternatively, in this case, the medium is said to have normal dispersion. Whereas, if the index increases with increasing wavelength, the medium is said to have anomalous dispersion, at the interface of such a material with air or vacuum, Snells law predicts that light incident at an angle θ to the normal will be refracted at an angle arcsin. Thus, blue light, with a refractive index, will be bent more strongly than red light
Dispersion (optics)
–
A
compact fluorescent lamp seen through an
Amici prism
Dispersion (optics)
–
In a
dispersive prism, material dispersion (a
wavelength -dependent
refractive index) causes different colors to
refract at different angles, splitting white light into a
rainbow.
23.
Copper
–
Copper is a chemical element with symbol Cu and atomic number 29. It is a soft, malleable, and ductile metal with high thermal and electrical conductivity. A freshly exposed surface of copper has a reddish-orange color. Copper is one of the few metals that occur in nature in directly usable metallic form as opposed to needing extraction from an ore and this led to very early human use, from c.8000 BC. Copper used in buildings, usually for roofing, oxidizes to form a green verdigris, Copper is sometimes used in decorative art, both in its elemental metal form and in compounds as pigments. Copper compounds are used as agents, fungicides, and wood preservatives. Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the enzyme complex cytochrome c oxidase. In molluscs and crustaceans, copper is a constituent of the blood pigment hemocyanin, replaced by the hemoglobin in fish. In humans, copper is found mainly in the liver, muscle, the adult body contains between 1.4 and 2.1 mg of copper per kilogram of body weight. The filled d-shells in these elements contribute little to interatomic interactions, unlike metals with incomplete d-shells, metallic bonds in copper are lacking a covalent character and are relatively weak. This observation explains the low hardness and high ductility of single crystals of copper, at the macroscopic scale, introduction of extended defects to the crystal lattice, such as grain boundaries, hinders flow of the material under applied stress, thereby increasing its hardness. For this reason, copper is supplied in a fine-grained polycrystalline form. The softness of copper partly explains its high conductivity and high thermal conductivity. The maximum permissible current density of copper in open air is approximately 3. 1×106 A/m2 of cross-sectional area, Copper is one of a few metallic elements with a natural color other than gray or silver. Pure copper is orange-red and acquires a reddish tarnish when exposed to air, as with other metals, if copper is put in contact with another metal, galvanic corrosion will occur. A green layer of verdigris can often be seen on old structures, such as the roofing of many older buildings. Copper tarnishes when exposed to sulfur compounds, with which it reacts to form various copper sulfides. There are 29 isotopes of copper, 63Cu and 65Cu are stable, with 63Cu comprising approximately 69% of naturally occurring copper, both have a spin of 3⁄2
Copper
–
Native copper (~4 cm in size)
Copper
–
A copper disc (99.95% pure) made by
continuous casting;
etched to reveal
crystallites.
Copper
–
Copper just above its melting point keeps its pink luster color when enough light outshines the orange
incandescence color.
Copper
–
Unoxidized copper wire (left) and oxidized copper wire (right).
24.
Mineral
–
A mineral is a naturally occurring chemical compound, usually of crystalline form and abiogenic in origin. A mineral has one specific chemical composition, whereas a rock can be an aggregate of different minerals or mineraloids, the study of minerals is called mineralogy. There are over 5,300 known mineral species, over 5,070 of these have been approved by the International Mineralogical Association, the silicate minerals compose over 90% of the Earths crust. The diversity and abundance of species is controlled by the Earths chemistry. Silicon and oxygen constitute approximately 75% of the Earths crust, which translates directly into the predominance of silicate minerals, minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various species, changes in the temperature, pressure, or bulk composition of a rock mass cause changes in its minerals. Minerals can be described by their various properties, which are related to their chemical structure. Common distinguishing characteristics include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, tenacity, cleavage, fracture, parting, more specific tests for describing minerals include magnetism, taste or smell, radioactivity and reaction to acid. Minerals are classified by key chemical constituents, the two dominant systems are the Dana classification and the Strunz classification, the silicate class of minerals is subdivided into six subclasses by the degree of polymerization in the chemical structure. All silicate minerals have a unit of a 4− silica tetrahedron—that is, a silicon cation coordinated by four oxygen anions. These tetrahedra can be polymerized to give the subclasses, orthosilicates, disilicates, cyclosilicates, inosilicates, phyllosilicates, other important mineral groups include the native elements, sulfides, oxides, halides, carbonates, sulfates, and phosphates. The first criterion means that a mineral has to form by a natural process, stability at room temperature, in the simplest sense, is synonymous to the mineral being solid. More specifically, a compound has to be stable or metastable at 25 °C, modern advances have included extensive study of liquid crystals, which also extensively involve mineralogy. Minerals are chemical compounds, and as such they can be described by fixed or a variable formula, many mineral groups and species are composed of a solid solution, pure substances are not usually found because of contamination or chemical substitution. Finally, the requirement of an ordered atomic arrangement is usually synonymous with crystallinity, however, crystals are also periodic, an ordered atomic arrangement gives rise to a variety of macroscopic physical properties, such as crystal form, hardness, and cleavage. There have been recent proposals to amend the definition to consider biogenic or amorphous substances as minerals. The formal definition of an approved by the IMA in 1995, A mineral is an element or chemical compound that is normally crystalline. However, if geological processes were involved in the genesis of the compound, Mineral classification schemes and their definitions are evolving to match recent advances in mineral science
Mineral
–
Amethyst, a variety of
quartz
Mineral
–
Schist is a
metamorphic rock characterized by an abundance of platy minerals. In this example, the rock has prominent
sillimanite porphyroblasts as large as 3 cm (1.2 in).
Mineral
–
Hübnerite, the manganese-rich end-member of the
wolframite series, with minor quartz in the background
Mineral
–
When minerals react, the products will sometimes assume the shape of the reagent; the product mineral is termed to be a pseudomorph of (or after) the reagent. Illustrated here is a pseudomorph of
kaolinite after
orthoclase. Here, the pseudomorph preserved the Carlsbad
twinning common in orthoclase.
25.
Lyon
–
Lyon or Lyons is a city in east-central France, in the Auvergne-Rhône-Alpes region, about 470 km from Paris and 320 km from Marseille. Inhabitants of the city are called Lyonnais, Lyon had a population of 506,615 in 2014 and is Frances third-largest city after Paris and Marseille. Lyon is the capital of the Metropolis of Lyon and the region of Auvergne-Rhône-Alpes, the metropolitan area of Lyon had a population of 2,237,676 in 2013, the second-largest in France after Paris. The city is known for its cuisine and gastronomy and historical and architectural landmarks and is a UNESCO World Heritage Site, Lyon was historically an important area for the production and weaving of silk. It played a significant role in the history of cinema, Auguste, the city is also known for its famous light festival, Fête des Lumières, which occurs every 8 December and lasts for four days, earning Lyon the title of Capital of Lights. Economically, Lyon is a centre for banking, as well as for the chemical, pharmaceutical. The city contains a significant software industry with a focus on video games. Lyon hosts the headquarters of Interpol, Euronews, and International Agency for Research on Cancer. Lyon was ranked 19th globally and second in France for innovation in 2014 and it ranked second in France and 39th globally in Mercers 2015 liveability rankings. These refugees had been expelled from Vienne by the Allobroges and were now encamped at the confluence of the Saône and Rhône rivers, dio Cassius says this task was to keep the two men from joining Mark Antony and bringing their armies into the developing conflict. The Roman foundation was at Fourvière hill and was officially called Colonia Copia Felix Munatia, a name invoking prosperity, the city became increasingly referred to as Lugdunum. The earliest translation of this Gaulish place-name as Desired Mountain is offered by the 9th-century Endlicher Glossary, in contrast, some modern scholars have proposed a Gaulish hill-fort named Lugdunon, after the Celtic god Lugus, and dúnon. It then became the capital of Gaul, partly due to its convenient location at the convergence of two rivers, and quickly became the main city of Gaul. Two emperors were born in city, Claudius, whose speech is preserved in the Lyon Tablet in which he justifies the nomination of Gallic senators. Today, the archbishop of Lyon is still referred to as Primat des Gaules, the Christians in Lyon were martyred for their beliefs under the reigns of various Roman emperors, most notably Marcus Aurelius and Septimus Severus. Local saints from this period include Blandina, Pothinus, and Epipodius, in the second century AD, the great Christian bishop of Lyon was the Easterner, Irenaeus. Burgundian refugees fleeing the destruction of Worms by the Huns in 437 were re-settled by the commander of the west, Aëtius. This became the capital of the new Burgundian kingdom in 461, in 843, by the Treaty of Verdun, Lyon, with the country beyond the Saône, went to Lothair I
Lyon
–
Top, the Basilique de Notre-Dame de Fourvière, the Place des Terreaux with the Fontaine Bartholdi and Lyon City Hall at night. Centre, the Parc de la Tête d'Or, the Confluence district and the old city. Bottom, the Pont Lafayette, the Part-Dieu district with the Place Bellecour in the foreground during the Festival of Lights.
Lyon
–
Place Carnot, Lyons
Lyon
–
The lion has been the symbol of the city for centuries and is represented throughout the city.
Lyon
–
Lyon in the 18th century
26.
France
–
France, officially the French Republic, is a country with territory in western Europe and several overseas regions and territories. The European, or metropolitan, area of France extends from the Mediterranean Sea to the English Channel and the North Sea, Overseas France include French Guiana on the South American continent and several island territories in the Atlantic, Pacific and Indian oceans. France spans 643,801 square kilometres and had a population of almost 67 million people as of January 2017. It is a unitary republic with the capital in Paris. Other major urban centres include Marseille, Lyon, Lille, Nice, Toulouse, during the Iron Age, what is now metropolitan France was inhabited by the Gauls, a Celtic people. The area was annexed in 51 BC by Rome, which held Gaul until 486, France emerged as a major European power in the Late Middle Ages, with its victory in the Hundred Years War strengthening state-building and political centralisation. During the Renaissance, French culture flourished and a colonial empire was established. The 16th century was dominated by civil wars between Catholics and Protestants. France became Europes dominant cultural, political, and military power under Louis XIV, in the 19th century Napoleon took power and established the First French Empire, whose subsequent Napoleonic Wars shaped the course of continental Europe. Following the collapse of the Empire, France endured a succession of governments culminating with the establishment of the French Third Republic in 1870. Following liberation in 1944, a Fourth Republic was established and later dissolved in the course of the Algerian War, the Fifth Republic, led by Charles de Gaulle, was formed in 1958 and remains to this day. Algeria and nearly all the colonies became independent in the 1960s with minimal controversy and typically retained close economic. France has long been a centre of art, science. It hosts Europes fourth-largest number of cultural UNESCO World Heritage Sites and receives around 83 million foreign tourists annually, France is a developed country with the worlds sixth-largest economy by nominal GDP and ninth-largest by purchasing power parity. In terms of household wealth, it ranks fourth in the world. France performs well in international rankings of education, health care, life expectancy, France remains a great power in the world, being one of the five permanent members of the United Nations Security Council with the power to veto and an official nuclear-weapon state. It is a member state of the European Union and the Eurozone. It is also a member of the Group of 7, North Atlantic Treaty Organization, Organisation for Economic Co-operation and Development, the World Trade Organization, originally applied to the whole Frankish Empire, the name France comes from the Latin Francia, or country of the Franks
France
–
One of the
Lascaux paintings: a horse –
Dordogne, approximately 18,000 BC
France
–
Flag
France
–
The
Maison Carrée was a temple of the
Gallo-Roman city of Nemausus (present-day
Nîmes) and is one of the best preserved vestiges of the
Roman Empire.
France
–
With
Clovis ' conversion to Catholicism in 498, the
Frankish monarchy,
elective and
secular until then, became
hereditary and of
divine right.
27.
Carbonate
–
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, a polyatomic ion with the formula of CO2−3. The name may mean an ester of carbonic acid, an organic compound containing the carbonate group C2. In geology and mineralogy, the term carbonate can refer both to carbonate minerals and carbonate rock, and both are dominated by the ion, CO2−3. Carbonate minerals are extremely varied and ubiquitous in chemically precipitated sedimentary rock, sodium carbonate and potassium carbonate have been used since antiquity for cleaning and preservation, as well as for the manufacture of glass. Carbonates are widely used in industry, e. g. in iron smelting, as a raw material for Portland cement and lime manufacture, in the composition of ceramic glazes, the carbonate ion is the simplest oxocarbon anion. It consists of one carbon atom surrounded by three oxygen atoms, in a planar arrangement, with D3h molecular symmetry. It has a mass of 60.01 g/mol and carries a total formal charge of −2. It is the base of the hydrogen carbonate ion, HCO−3. The Lewis structure of the ion has two single bonds to negative oxygen atoms, and one short double bond to a neutral oxygen. This structure is incompatible with the symmetry of the ion. This process is called calcination, after calx, the Latin name of quicklime or calcium oxide, CaO, exceptions include lithium, sodium, potassium and ammonium carbonates, as well as many uranium carbonates. In aqueous solution, carbonate, bicarbonate, carbon dioxide, in strongly basic conditions, the carbonate ion predominates, while in weakly basic conditions, the bicarbonate ion is prevalent. In more acid conditions, aqueous carbon dioxide, CO2, is the main form, thus sodium carbonate is basic, sodium bicarbonate is weakly basic, while carbon dioxide itself is a weak acid. Carbonated water is formed by dissolving CO2 in water under pressure, in living systems an enzyme, carbonic anhydrase, speeds the interconversion of CO2 and carbonic acid. Although the carbonate salts of most metals are insoluble in water, in solution this equilibrium between carbonate, bicarbonate, carbon dioxide and carbonic acid changes consonant to changing temperature and pressure conditions. In the case of ions with insoluble carbonates, e. g. CaCO3. This is an explanation for the buildup of scale inside pipes caused by hard water, in organic chemistry a carbonate can also refer to a functional group within a larger molecule that contains a carbon atom bound to three oxygen atoms, one of which is double bonded. These compounds are known as organocarbonates or carbonate esters, and have the general formula ROCOOR′
Carbonate
–
Carbonate
28.
Pliny the Elder
–
In the latter number will be my uncle, by virtue of his own and of your compositions. Pliny is referring to the fact that Tacitus relied on his uncles now missing work on the History of the German Wars. The wind caused by the sixth and largest pyroclastic surge of the eruption would not allow his ship to leave the shore, and Pliny probably died during this event. Plinys dates are pinned to the eruption of Mount Vesuvius in AD79 and a statement of his nephew that he died in his 56th year, Pliny was the son of an equestrian, Gaius Plinius Celer, and his wife, Marcella. Neither the younger nor the elder Pliny mention the names and their ultimate source is a fragmentary inscription found in a field in Verona and recorded by the 16th century Augustinian monk Onofrio Panvinio at Verona. The reading of the inscription depends on the reconstruction, but in all cases the names come through, whether he was an augur and whether she was named Grania Marcella are less certain. Jean Hardouin presents a statement from a source that he claims was ancient, that Pliny was from Verona. Hardouin also cites the conterraneity of Catullus, additional efforts to connect Celer and Marcella with other gentes are highly speculative. Hardouin is the scholar to use his unknown source. He kept statues of his ancestors there, a statue of Pliny on the facade of the Duomo of Como celebrates him as a native son. He had a sister, Plinia, who married into the Caecilii and was the mother of his nephew, Pliny the Younger, whose letters describe his work and study regimen in detail. In one of his letters to Tacitus, Pliny the Younger details how his uncles breakfasts would be light and simple following the customs of our forefathers. This shows that Pliny the Younger wanted it to be conveyed that Pliny the Elder was a good Roman and this statement would have pleased Tacitus. Two inscriptions identifying the hometown of Pliny the Younger as Como take precedence over the Verona theory, one commemorates the youngers career as imperial magistrate and details his considerable charitable and municipal expenses on behalf of the people of Como. Another identifies his father Lucius village as Fecchio near Como and it is likely therefore that Plinia was a local girl and Pliny the Elder, her brother, was from Como. Gaius was a member of the Plinii gens and he did not take his fathers cognomen, Celer, but assumed his own, Secundus. As his adopted son took the same cognomen, Pliny founded a branch, no earlier instances of the Plinii are known. In 59 BC, only about 82 years before Plinys birth, Julius Caesar founded Novum Comum as a colonia to secure the region against the Alpine tribes, whom he had been unable to defeat
Pliny the Elder
–
One of the
Xanten Horse-Phalerae located in the
British Museum, measuring 10.5 cm (4.1 in). It bears an inscription formed from punched dots: PLINIO PRAEF EQ; i.e., Plinio praefecto equitum, "Pliny prefect of cavalry". It was perhaps issued to every man in Pliny's unit. The figure is the bust of the emperor.
Pliny the Elder
–
Pliny the Elder, as imagined by a 19th-century artist. No contemporary depiction of Pliny is known to survive.
Pliny the Elder
–
City and Lake of
Como, painted by
Jean-Baptiste-Camille Corot, 1834.
Pliny the Elder
–
The temple of
Castor and Pollux in Rome
29.
Natural History (Pliny)
–
The Natural History is an early encyclopedia in Latin by Pliny the Elder, a Roman author and naval commander who died in 79 AD. It is one of the largest single works to have survived from the Roman Empire to the modern day, the works subject area is thus not limited to what is today understood by natural history, Pliny himself defines his scope as the natural world, or life. The work is divided into 37 books, organised into ten volumes, the Natural History became a model for later encyclopedias and scholarly works as a result of its breadth of subject matter, its referencing of original authors, and its index. The work is dedicated to the emperor Titus, son of Plinys close friend and it is the only work by Pliny to have survived and the last that he published. He began it in 77, and had not made a revision at the time of his death during the AD79 eruption of Vesuvius. Plinys Natural History was written alongside other substantial works, Pliny combined his scholarly activities with a busy career as an imperial administrator for the emperor Vespasian. Pliny claims to be the only Roman ever to have such a work, in his prayer for the blessing of the universal mother, Hail to thee, Nature. And do thou deign to show thy favour unto me, who, alone of all the citizens of Rome, have, in thy every department, the Natural History is encyclopaedic in scope, but its format is unlike a modern encyclopaedia. However, it does have structure, Pliny uses Aristotles division of nature to recreate the world in literary form. The work is unified but varied, My subject is the world of nature, or in other words, life, he tells Titus. Nature for Pliny was divine, a concept inspired by the Stoic philosophy which underlies much of his thought. But the deity in question was a goddess whose main purpose was to serve the human race, nature, that is life is human life in a natural landscape. After an initial survey of cosmology and geography, Pliny starts his treatment of animals with the human race and this teleological view of nature was common in antiquity and is crucial to the understanding of the Natural History. The components of nature are not just described in and for themselves, Pliny devotes a number of the books to plants, with a focus on their medicinal value, the books on minerals include descriptions of their uses in architecture, sculpture, painting and jewellery. Plinys premise is distinct from modern ecological theories, reflecting the sentiment of his time. Pliny repeated Aristotles maxim that Africa was always producing something new, natures variety and versatility were claimed to be infinite, When I have observed nature she has always induced me to deem no statement about her incredible. This led Pliny to recount rumours of strange peoples on the edges of the world and these monstrous races – the Cynocephali or Dog-Heads, the Sciapodae, whose single foot could act as a sunshade, the mouthless Astomi, who lived on scents – were not strictly new. They had been mentioned by the Greek historian Herodotus in the 5th century BC, Pliny had gone to investigate the strange cloud – shaped like an umbrella pine, according to his nephew – rising from the mountain
Natural History (Pliny)
–
Naturalis Historia, 1669 edition, title page. The title at the top reads: "Volume I of the Natural History of Gaius Plinius Secundus"; the ending -ae is a genitive ("of...").
Natural History (Pliny)
–
Naturalis Historia, work printed by Johannes Alvisius in 1499 in
Venice, Italy
Natural History (Pliny)
–
A
cynocephalus, or dog-head, as described by Pliny in his Natural History. From the
Nuremberg Chronicle (1493).
Natural History (Pliny)
–
A
sciapod, described by Pliny in his Natural History. From the
Nuremberg Chronicle (1493).
30.
Azure (color)
–
Azure is a variation of blue that is often described as the color of the sky on a clear day. On the RGB color wheel, azure is defined as the color at 210 degrees, in the RGB color model, used to create all the colors on a television or computer screen, azure is created by adding a little green light to blue light. The complementary color of azure is neon orange, in the X11 color system which became a standard for early web colors, azure is depicted as a pale cyan. The color azure ultimately takes its name from the blue mineral lapis lazuli. The name of the came to be associated with its color. Azure also describes the color of the mineral azurite, both in its form and as a pigment in various paint formulations. In order to preserve its deep color, azurite was ground coarsely, fine-ground azurite produces a lighter, washed-out color. Traditionally, the pigment was considered unstable in oil paints, and was isolated from other colors. Modern investigation of old paintings, however, shows that the pigment is very stable unless exposed to sulfur fumes, the use of the term spread through the practice of heraldry, where azure represents a blue color in the system of tinctures. In engravings, it is represented as a region of horizontal lines. In practice, azure has been represented by any number of shades of blue, in later heraldic practice a lighter blue, called bleu celeste, is sometimes specified. All of the colors shown below in the variations of azure are referenced as having a hue code of between 195 and 225, signifying that these colors are tones of azure. The only exception, as noted below, is the web color azure which, displayed at right is the web color called azure, in actuality it is a pale pastel tint of cyan, as can be ascertained by noting its hue angle of 180 degrees. In an artistic context, this color would be called azure mist, the web color Alice blue is a pale tint of azure. Displayed at right is the web color sky blue. Baby blue is known as one of the pastel colors and this color is associated with baby boys in Western culture. The first recorded use of blue as a color name in English was in 1892. Displayed at right is the web color sky blue, the first recorded use of sky blue as a color name in English was in 1728 in the Cyclopædia of Ephraim Chambers
Azure (color)
–
Azure
Azure (color)
–
Azure- pigment
Azure (color)
–
A slab of
lapis lazuli, the mineral from which azure took its name
Azure (color)
–
Rough and polished
Lapis lazuli.
31.
Arabic language
–
Arabic is a Central Semitic language that was first spoken in Iron Age northwestern Arabia and is now the lingua franca of the Arab world. Arabic is also the language of 1.7 billion Muslims. It is one of six languages of the United Nations. The modern written language is derived from the language of the Quran and it is widely taught in schools and universities, and is used to varying degrees in workplaces, government, and the media. The two formal varieties are grouped together as Literary Arabic, which is the language of 26 states. Modern Standard Arabic largely follows the standards of Quranic Arabic. Much of the new vocabulary is used to denote concepts that have arisen in the post-Quranic era, Arabic has influenced many languages around the globe throughout its history. During the Middle Ages, Literary Arabic was a vehicle of culture in Europe, especially in science, mathematics. As a result, many European languages have borrowed many words from it. Many words of Arabic origin are found in ancient languages like Latin. Balkan languages, including Greek, have acquired a significant number of Arabic words through contact with Ottoman Turkish. Arabic has also borrowed words from languages including Greek and Persian in medieval times. Arabic is a Central Semitic language, closely related to the Northwest Semitic languages, the Ancient South Arabian languages, the Semitic languages changed a great deal between Proto-Semitic and the establishment of the Central Semitic languages, particularly in grammar. Innovations of the Central Semitic languages—all maintained in Arabic—include, The conversion of the suffix-conjugated stative formation into a past tense, the conversion of the prefix-conjugated preterite-tense formation into a present tense. The elimination of other prefix-conjugated mood/aspect forms in favor of new moods formed by endings attached to the prefix-conjugation forms, the development of an internal passive. These features are evidence of descent from a hypothetical ancestor. In the southwest, various Central Semitic languages both belonging to and outside of the Ancient South Arabian family were spoken and it is also believed that the ancestors of the Modern South Arabian languages were also spoken in southern Arabia at this time. To the north, in the oases of northern Hijaz, Dadanitic and Taymanitic held some prestige as inscriptional languages, in Najd and parts of western Arabia, a language known to scholars as Thamudic C is attested
Arabic language
–
The Galland Manuscript of
One Thousand and One Nights, 14th century
Arabic language
–
al-ʿArabiyyah in written Arabic (
Naskh script)
Arabic language
–
Bilingual traffic sign in
Qatar.
Arabic language
–
Examples of how the Arabic root and form system works.
32.
Persian language
–
Persian, also known by its endonym Farsi, is one of the Western Iranian languages within the Indo-Iranian branch of the Indo-European language family. It is primarily spoken in Iran, Afghanistan, and Tajikistan and it is mostly written in the Persian alphabet, a modified variant of the Arabic script. Its grammar is similar to that of many contemporary European languages, Persian gets its name from its origin at the capital of the Achaemenid Empire, Persis, hence the name Persian. A Persian-speaking person may be referred to as Persophone, there are approximately 110 million Persian speakers worldwide, with the language holding official status in Iran, Afghanistan, and Tajikistan. For centuries, Persian has also been a cultural language in other regions of Western Asia, Central Asia. It also exerted influence on Arabic, particularly Bahrani Arabic. Persian is one of the Western Iranian languages within the Indo-European family, other Western Iranian languages are the Kurdish languages, Gilaki, Mazanderani, Talysh, and Balochi. Persian is classified as a member of the Southwestern subgroup within Western Iranian along with Lari, Kumzari, in Persian, the language is known by several names, Western Persian, Parsi or Farsi has been the name used by all native speakers until the 20th century. Since the latter decades of the 20th century, for reasons, in English. Tajiki is the variety of Persian spoken in Tajikistan and Uzbekistan by the Tajiks, according to the Oxford English Dictionary, the term Persian as a language name is first attested in English in the mid-16th century. Native Iranian Persian speakers call it Fārsi, Farsi is the Arabicized form of Pārsi, subsequent to Muslim conquest of Persia, due to a lack of the phoneme /p/ in Standard Arabic. The origin of the name Farsi and the place of origin of the language which is Fars Province is the Arabicized form of Pārs, in English, this language has historically been known as Persian, though Farsi has also gained some currency. Farsi is encountered in some literature as a name for the language. In modern English the word Farsi refers to the language while Parsi describes Zoroastrians, some Persian language scholars such as Ehsan Yarshater, editor of Encyclopædia Iranica, and University of Arizona professor Kamran Talattof, have also rejected the usage of Farsi in their articles. The international language-encoding standard ISO 639-1 uses the code fa, as its system is mostly based on the local names. The more detailed standard ISO 639-3 uses the name Persian for the dialect continuum spoken across Iran and Afghanistan and this consists of the individual languages Dari and Iranian Persian. Currently, Voice of America, BBC World Service, Deutsche Welle, Radio Free Europe/Radio Liberty also includes a Tajik service and an Afghan service. This is also the case for the American Association of Teachers of Persian, The Centre for Promotion of Persian Language and Literature, Persian is an Iranian language belonging to the Indo-Iranian branch of the Indo-European family of languages
Persian language
–
Old Persian
Persian language
–
Ferdowsi 's
Shahnameh
Persian language
–
Kalilah va Dimna, an influential work in Persian literature.
33.
Lapis lazuli
–
Lapis lazuli, or lapis for short, is a deep blue, semi-precious stone prized since antiquity for its intense color. As early as the 7th millennium BC, lapis lazuli was mined in the Sar-i Sang mines, in Shortugai, Lapis was highly valued by the Indus Valley Civilisation. Lapis beads have been found at burials in Mehrgarh, the Caucasus. It was used in the mask of Tutankhamun. At the end of the Middle Ages, lapis lazuli began to be exported to Europe, where it was ground into powder and made into ultramarine, today, mines in northeast Afghanistan and Pakistan are still the major source of lapis lazuli. Important amounts are produced from mines west of Lake Baikal in Russia. Smaller quantities are mined in Italy, Mongolia, the United States, the name Lapis lazuli came to be associated with its color. The English word azure, French azur, Italian azzurro, Polish lazur, Romanian azur and azuriu, Portuguese and Spanish azul, the most important mineral component of lapis lazuli is lazurite, a feldspathoid silicate mineral with the formula 861-2. Most lapis lazuli also contains calcite, sodalite, and pyrite, some samples of lapis lazuli contain augite, diopside, enstatite, mica, hauynite, hornblende, nosean, and sulfur-rich löllingite geyerite. Lapis lazuli usually occurs in marble as a result of contact metamorphism. The intense blue color is due to the presence of the radical anion in the crystal. An electronic excitation of one electron from the highest doubly filled molecular orbital into the lowest singly occupied orbital results in an intense absorption line at λmax ~617 nm. Lapis lazuli is found in limestone in the Kokcha River valley of Badakhshan province in northeastern Afghanistan, Afghanistan was the source of lapis for the ancient Egyptian and Mesopotamian civilizations, as well as the later Greeks and Romans. Ancient Egyptians obtained this material through trade from Afghanistan, during the height of the Indus Valley Civilisation about 2000 BC, the Harappan colony now known as Shortugai was established near the lapis mines. In addition to the Afghan deposits, lapis is also extracted in the Andes and it is mined in smaller amounts in Angola, Argentina, Burma, Pakistan, Canada, Italy, India, and in the United States in California and Colorado. Lapis takes an excellent polish and can be made into jewelry, carvings, boxes, mosaics, ornaments, small statues, during the Renaissance, Lapis was ground and processed to make the pigment ultramarine for use in frescoes and oil painting. Its usage as a pigment in oil paint largely ended in the early 19th century when a chemically identical synthetic variety became available, Lapis lazuli is commercially synthesized or simulated by the Gilson process, which is used to make artificial ultramarine and hydrous zinc phosphates. It may also be substituted by spinel or sodalite, or by dyed jasper or howlite, Lapis lazuli has been mined in Afghanistan and exported to the Mediterranean world and South Asia since the Neolithic age
Lapis lazuli
–
Lapis lazuli from Afghanistan in its natural state
Lapis lazuli
–
A sample from the Sar-i Sang mine in Afghanistan, where lapis lazuli has been mined since the 7th Millennium BCE.
Lapis lazuli
–
A polished block of lapis lazuli
Lapis lazuli
–
Natural ultramarine pigment made from ground lapis lazuli. This was the most expensive blue pigment during the
Renaissance, often reserved for depicting the robes of
Angels or the
Virgin Mary.
34.
Carbonate minerals
–
IMA-CNMNC proposes a new hierarchical scheme. This list uses the Classification of Nickel–Strunz
Carbonate minerals
–
Calcite crystals from the Sweetwater Mine, Viburnum Trend District,
Reynolds County, Missouri - 6.2 × 6 × 3.3 cm
Carbonate minerals
–
Rhodochrosite, Sweet Home Mine, Alma, Colorado - 5.2 × 4.2 × 2.3 cm
Carbonate minerals
–
Smithsonite, Silver Bill Mine, Dragoon Mts,
Cochise County, Arizona - 4.8 × 4.1 × 2.4 cm
Carbonate minerals
–
Dolomite with calcite and chalcopyrite from the Picher Field,
Tri-State district,
Cherokee County, Kansas; 12.0 × 9.7 × 4.3 cm
35.
Malachite
–
Malachite is a copper carbonate hydroxide mineral, with the formula Cu2CO32. Individual crystals are rare but do occur as slender to acicular prisms, pseudomorphs after more tabular or blocky azurite crystals also occur. The stones name derives from Greek Μολοχίτης λίθος molochitis lithos, mallow-green stone, from μολόχη molōchē, variant of μαλάχη malāchē, the mineral was given this name due to its resemblance to the leaves of the mallow plant. Archeological evidence indicates that the mineral has been mined and smelted to obtain copper at Timna Valley in Israel for over 3,000 years, since then, malachite has been used as both an ornamental stone and as a gemstone. In ancient Egypt the colour green was associated with death and the power of resurrection as well as new life and they believed that the afterlife contained an eternal paradise which resembled their lives but with no pain or suffering, and referred to this place as the ‘Field of Malachite’. Malachite was used as a pigment in green paints from antiquity until about 1800. The pigment is moderately lightfast, very sensitive to acids, and this natural form of green pigment has been replaced by its synthetic form, verditer, among other synthetic greens. Malachite is also used for decorative purposes, such as in the Malachite Room in the Hermitage, which features a huge malachite vase, and the Malachite Room in Castillo de Chapultepec in Mexico City. The Tazza, a large vase, one of the largest pieces of malachite in North America. Malachite often results from the weathering of copper ores, and is found together with azurite, goethite. Except for its vibrant green color, the properties of malachite are similar to those of azurite, Malachite is more common than azurite and is typically associated with copper deposits around limestones, the source of the carbonate. Large quantities of malachite have been mined in the Urals, Russia, ural malachite is not being mined at present, but G. N Vertushkova reports the possible discovery of new deposits of malachite in the Urals. Virtual tour of the Malachite Room Malachite, Colourlex
Malachite
–
Malachite from the
Democratic Republic of the Congo
Malachite
–
Slice through a double
stalactite, from
Kolwezi, Democratic Republic of the Congo. Size 5.9 × 3.9 × 0.7 cm.
Malachite
–
A polished slab of malachite, from the Democratic Republic of the Congo
Malachite
–
Malachite and
azurite, from
Morenci, Arizona USA. Size 4.4×4.1×2.2 cm.
36.
Copper(II) carbonate
–
Copper carbonate or cupric carbonate is a chemical compound with formula CuCO3. At ambient temperatures, is a solid consisting of copper cations Cu2+. This compound is rarely encountered because it is difficult to prepare, the terms copper carbonate, copper carbonate, and cupric carbonate almost always refer to a basic copper carbonate, such as Cu 22CO3 or Cu 322. For this reason, the neutral may be used instead of basic to refer specifically CuCO3. Thermal decomposition of the basic carbonate at atmospheric pressure yields copper oxide CuO rather than the carbonate. In 1960, C. W. F. T. Pistorius claimed synthesis by heating basic copper carbonate at 180 °C in an atmosphere of carbon dioxide CO2 and water for 36 hours. The bulk of the products was well-crystallized malachite Cu 2CO32, however, this synthesis apparently was not reproduced. Reliable synthesis of copper carbonate was reported for the first time in 1973 by Hartmut Ehrhardt. The compound was obtained as a powder, by heating basic copper carbonate in an atmosphere of carbon dioxide at 500 °C and 2 GPa. The compound was determined to have the monoclinic structure, the stability of dry CuCO3 depends critically on the partial pressure of carbon dioxide. It is stable for months in dry air, but should actually decompose slowly into CuO, in the presence of water or moist air at 25 °C, CuCO3 is stable only for pCO2 above 4.57 atmospheres and pH between about 4 and 8. Below that pressure, it reacts with water to form a basic carbonate, in highly basic solutions, the complex anion Cu22− is formed instead. The solubility product of the true copper carbonate was measured by Reiterer and others as pKso =11.45 ±0.10 at 25 °C
Copper(II) carbonate
–
Basic copper carbonate
Copper(II) carbonate
–
Basic copper(II) carbonate
patina on roofs of
Château Frontenac.
37.
Cation
–
An ion is an atom or a molecule in which the total number of electrons is not equal to the total number of protons, giving the atom or molecule a net positive or negative electrical charge. Ions can be created, by chemical or physical means. In chemical terms, if an atom loses one or more electrons. If an atom gains electrons, it has a net charge and is known as an anion. Ions consisting of only a single atom are atomic or monatomic ions, because of their electric charges, cations and anions attract each other and readily form ionic compounds, such as salts. In the case of ionization of a medium, such as a gas, which are known as ion pairs are created by ion impact, and each pair consists of a free electron. The word ion comes from the Greek word ἰόν, ion, going and this term was introduced by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that goes from one electrode to the other through an aqueous medium. Faraday also introduced the words anion for a charged ion. In Faradays nomenclature, cations were named because they were attracted to the cathode in a galvanic device, arrhenius explanation was that in forming a solution, the salt dissociates into Faradays ions. Arrhenius proposed that ions formed even in the absence of an electric current, ions in their gas-like state are highly reactive, and do not occur in large amounts on Earth, except in flames, lightning, electrical sparks, and other plasmas. These gas-like ions rapidly interact with ions of charge to give neutral molecules or ionic salts. These stabilized species are commonly found in the environment at low temperatures. A common example is the present in seawater, which are derived from the dissolved salts. Electrons, due to their mass and thus larger space-filling properties as matter waves, determine the size of atoms. Thus, anions are larger than the parent molecule or atom, as the excess electron repel each other, as such, in general, cations are smaller than the corresponding parent atom or molecule due to the smaller size of its electron cloud. One particular cation contains no electrons, and thus consists of a single proton - very much smaller than the parent hydrogen atom. Since the electric charge on a proton is equal in magnitude to the charge on an electron, an anion, from the Greek word ἄνω, meaning up, is an ion with more electrons than protons, giving it a net negative charge. A cation, from the Greek word κατά, meaning down, is an ion with fewer electrons than protons, there are additional names used for ions with multiple charges
Cation
38.
Hydroxide
–
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a covalent bond and it is an important but usually minor constituent of water. It functions as a base, a ligand, a nucleophile, the hydroxide ion forms salts, some of which dissociate in aqueous solution, liberating solvated hydroxide ions. Sodium hydroxide is a multi-million-ton per annum commodity chemical, a hydroxide attached to a strongly electropositive center may itself ionize, liberating a hydrogen cation, making the parent compound an acid. The corresponding electrically neutral compound •HO is the hydroxyl radical, the corresponding covalently-bound group –OH of atoms is the hydroxyl group. Hydroxide ion and hydroxyl group are nucleophiles and can act as a catalyst in organic chemistry, many inorganic substances which bear the word hydroxide in their names are not ionic compounds of the hydroxide ion, but covalent compounds which contain hydroxyl groups. The pH of a solution is equal to the decimal cologarithm of the cation concentration. The concentration of ions can be expressed in terms of pOH. Addition of a base to water will reduce the hydrogen cation concentration, POH can be kept at a nearly constant value with various buffer solutions. In aqueous solution the hydroxide ion is a base in the Brønsted–Lowry sense as it can accept a proton from a Brønsted–Lowry acid to form a water molecule and it can also act as a Lewis base by donating a pair of electrons to a Lewis acid. In aqueous solution both hydrogen and hydroxide ions are solvated, with hydrogen bonds between oxygen and hydrogen atoms. Indeed, the bihydroxide ion H 3O−2 has been characterized in the solid state and this compound is centrosymmetric and has a very short hydrogen bond that is similar to the length in the bifluoride ion HF−2. In aqueous solution the hydroxide ion forms strong bonds with water molecules. A consequence of this is that concentrated solutions of sodium hydroxide have high viscosity due to the formation of a network of hydrogen bonds as in hydrogen fluoride solutions. In solution, exposed to air, the ion reacts rapidly with atmospheric carbon dioxide, acting as an acid, to form, initially. OH− + CO2 ⇌ HCO−3 The equilibrium constant for this reaction can be specified either as a reaction with dissolved carbon dioxide or as a reaction with carbon dioxide gas. At neutral or acid pH, the reaction is slow, but is catalyzed by the carbonic anhydrase. Solutions containing the hydroxide ion attack glass, in this case, the silicates in glass are acting as acids
Hydroxide
–
Hydroxide
39.
Copper sulfate
–
Copper sulfate, also known as cupric sulfate, or copper sulphate, is the inorganic compound with the chemical formula CuSO4x, where x can range from 0 to 5. The pentahydrate is the most common form, older names for this compound include blue vitriol, bluestone, vitriol of copper, and Roman vitriol. The pentahydrate, the most commonly encountered salt, is bright blue and it exothermically dissolves in water to give the aquo complex 2+, which has octahedral molecular geometry. The structure of the solid pentahydrate reveals a structure wherein copper is again octahedral. The Cu4 centers are interconnected by sulfate anions to form chains, anhydrous copper sulfate is a white powder. Copper sulfate is produced industrially by treating copper metal with hot concentrated sulfuric acid or its oxides with dilute sulfuric acid, for laboratory use, copper sulfate is usually purchased. Copper sulfate can also be produced by slowly leaching low grade ore in air. Commercial copper sulfate is usually about 98% pure copper sulfate, and may contain traces of water. Anhydrous Copper sulfate is 39.81 percent copper and 60.19 percent sulfate by mass, four types of crystal size are provided based on its usage, large crystals, small crystals, snow crystals, and windswept powder. Copper sulfate pentahydrate decomposes before melting and it loses two water molecules upon heating at 63 °C, followed by two more at 109 °C and the final water molecule at 200 °C. Dehydration proceeds by decomposition of the moiety, two opposing aqua groups are lost to give a diaquacopper moiety. The second dehydration step occurs with the final two groups are lost. Complete dehydration occurs when the only unbound water molecule is lost, at 650 °C, copper sulfate decomposes into copper oxide and sulfur trioxide. Copper sulfate reacts with concentrated acid to give tetrachlorocuprate, Cu2+ +4 Cl− → CuCl2−4 Copper sulfate is commonly included in childrens chemistry sets. It is often used to grow crystals in schools and in copper plating experiments, Copper sulfate is often used to demonstrate an exothermic reaction, in which steel wool or magnesium ribbon is placed in an aqueous solution of CuSO4. It is used to demonstrate the principle of mineral hydration, the pentahydrate form, which is blue, is heated, turning the copper sulfate into the anhydrous form which is white, while the water that was present in the pentahydrate form evaporates. When water is added to the anhydrous compound, it turns back into the pentahydrate form, regaining its blue color. Copper sulfate pentahydrate can easily be produced by crystallization from solution as copper sulfate is quite hygroscopic, in an illustration of a single metal replacement reaction, iron is submerged in a solution of copper sulfate
Copper sulfate
–
Anhydrous CuSO 4 powder
Copper sulfate
–
Crystals of CuSO 4 ·5H 2 O
Copper sulfate
–
Preparation of copper (II) sulfate by electrolyzing sulfuric acid, using copper electrodes
Copper sulfate
–
The rare mineral boothite (CuSO 4 ·7H 2 O)
40.
Saturated solution
–
In chemistry, saturation has diverse meanings, all based on the idea of reaching a maximum capacity. In organic chemistry, a compound is a hydrocarbon which has no double or triple bonds. For example, consider three similar organic compounds that are less saturated, ethane, ethylene, and ethyne. Ethane, a saturated compound, has only single bonds between its hydrogen and carbon atoms. Ethylene, a compound of ethane, has a carbon double bond. Finally ethyne, the completely unsaturated compound of ethane, has a triple bond. The concept of saturation can be described using various naming systems, formulas, for instance, IUPAC nomenclature is a system of naming conventions used to describe the type and location of unsaturation within organic compounds. The degree of unsaturation is a used to summarize and diagram the amount of hydrogen that a compound can bind. Unsaturation can be determined by NMR, mass spectrometry and IR spectroscopy, tallow consists mainly of triglycerides, whose major constituents are derived from the saturated stearic and monounsaturated oleic acids. Many vegetable oils contain fatty acids with one or more double bonds in them, in organometallic chemistry, an unsaturated complex has fewer than 18 valence electrons and thus is susceptible to oxidative addition or coordination of an additional ligand. Unsaturation is characteristic of many catalysts because it is usually a requirement for substrate activation, in contrast, a coordinatively saturated complex resists undergoing substitution and oxidative addition reactions. In physical chemistry, saturation is the point at which the solute of a substance can dissolve no more of that substance and additional amounts of it will appear as a separate phase. This point of concentration, the saturation point, depends on the temperature and pressure of the solution as well as the chemical nature of the substances involved. Impurities, being present in lower concentration, do not saturate the solvent. If a change in conditions means that the concentration is higher than the saturation point. In physical chemistry, when referring to processes, saturation denotes the degree at which a binding site is fully occupied. For example, base refers to the fraction of exchangeable cations that are base cations. In biochemistry, the saturation refers to the fraction of total protein binding sites that are occupied at any given time
Saturated solution
–
Tallow consists mainly of triglycerides (fats), whose major constituents are derived from the saturated
stearic and monounsaturated
oleic acids.
41.
Sodium carbonate
–
Sodium carbonate, Na2CO3, is the water-soluble sodium salt of carbonic acid. It most commonly occurs as a crystalline decahydrate, which readily effloresces to form a white powder, pure sodium carbonate is a white, odorless powder that is hygroscopic. It has a strongly alkaline taste, and forms a basic solution in water. Sodium carbonate is known domestically for its everyday use as a water softener. Historically it was extracted from the ashes of plants growing in soils, such as vegetation from the Middle East, kelp from Scotland. Because the ashes of these plants were noticeably different from ashes of timber. It is synthetically produced in quantities from salt and limestone by a method known as the Solvay process. The manufacture of glass is one of the most important uses of sodium carbonate, Sodium carbonate acts as a flux for silica, lowering the melting point of the mixture to something achievable without special materials. This soda glass is mildly water-soluble, so some calcium carbonate is added to the mixture to make the glass produced insoluble. This type of glass is known as soda lime glass, soda for the sodium carbonate, soda lime glass has been the most common form of glass for centuries. Sodium carbonate is used as a relatively strong base in various settings. For example, it is used as a pH regulator to maintain stable alkaline conditions necessary for the action of the majority of film developing agents. It acts as an alkali because when dissolved in water, it dissociates into the acid, carbonic acid. This gives sodium carbonate in solution the ability to attack such as aluminium with the release of hydrogen gas. It is an additive in swimming pools used to raise the ph which can be lowered by chlorine tablets. In cooking, it is used in place of sodium hydroxide for lyeing, especially with German pretzels. These dishes are treated with a solution of a substance to change the pH of the surface of the food. In chemistry, it is used as an electrolyte
Sodium carbonate
–
Sodium carbonate
Sodium carbonate
42.
Mohs hardness
–
The Mohs scale of mineral hardness is a qualitative ordinal scale characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. Created in 1812 by German geologist and mineralogist Friedrich Mohs, it is one of several definitions of hardness in materials science, while greatly facilitating the identification of minerals in the field, the Mohs scale does not show how well hard materials perform in an industrial setting. Despite its lack of precision, the Mohs scale is highly relevant for field geologists, the Mohs scale hardness of minerals can be commonly found in reference sheets. Reference materials may be expected to have a uniform Mohs hardness, the Mohs scale of mineral hardness is based on the ability of one natural sample of mineral to scratch another mineral visibly. The samples of matter used by Mohs are all different minerals, Minerals are pure substances found in nature. Rocks are made up of one or more minerals, as the hardest known naturally occurring substance when the scale was designed, diamonds are at the top of the scale. The hardness of a material is measured against the scale by finding the hardest material that the material can scratch. For example, if material is scratched by apatite but not by fluorite. Scratching a material for the purposes of the Mohs scale means creating non-elastic dislocations visible to the naked eye, frequently, materials that are lower on the Mohs scale can create microscopic, non-elastic dislocations on materials that have a higher Mohs number. The Mohs scale is an ordinal scale. For example, corundum is twice as hard as topaz, the table below shows the comparison with the absolute hardness measured by a sclerometer, with pictorial examples. On the Mohs scale, a streak plate has a hardness of 7.0, using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale. The table below incorporates additional substances that may fall between levels, Comparison between Hardness and Hardness, Mohs hardness of elements is taken from G. V, samsonov in Handbook of the physicochemical properties of the elements, IFI-Plenum, New York, USA,1968. The Hardness of Minerals and Rocks
Mohs hardness
Mohs hardness
Mohs hardness
Mohs hardness
43.
Coordination complex
–
Many metal-containing compounds, especially those of transition metals, are coordination complexes. A coordination complex whose centre is an atom is called a metal complex. Coordination complexes are so pervasive that their structures and reactions are described in many ways, the atom within a ligand that is bonded to the central metal atom or ion is called the donor atom. In a typical complex, an ion is bonded to several donor atoms. A polydentate ligand is a molecule or ion that bonds to the atom through several of the ligands atoms. These complexes are called chelate complexes, the formation of complexes is called chelation, complexation. The central atom or ion, together with all ligands comprise the coordination sphere, the central atoms or ion and the donor atoms comprise the first coordination sphere. Coordination refers to the covalent bonds between the ligands and the central atom. Originally, a complex implied a reversible association of molecules, atoms, as applied to coordination chemistry, this meaning has evolved. Some metal complexes are formed virtually irreversibly and many are bound together by bonds that are quite strong, the number of donor atoms attached to the central atom or ion is called the coordination number. The most common coordination numbers are 2,4 and especially 6, for example, the cobalt hexahydrate ion or the hexaaquacobalt ion 2+, is a hydrated-complex ion that consists of six water molecules attached to a metal ion Co. The oxidation state and the number reflect the number of bonds formed between the metal ion and the ligands in the complex ion. However the coordination number of Pt2+ 2is 4 since it has two ligands, which contain four donor atoms in total. Coordination complexes have been known since the beginning of modern chemistry, early well-known coordination complexes include dyes such as Prussian blue. Their properties were first well understood in the late 1800s, following the 1869 work of Christian Wilhelm Blomstrand, Blomstrand developed what has come to be known as the complex ion chain theory. The theory claimed that the reason coordination complexes form is because in solution and he compared this effect to the way that various carbohydrate chains form. Following this theory, Danish scientist Sophus Mads Jorgensen made improvements to it and it was not until 1893 that the most widely accepted version of the theory today was published by Alfred Werner. Werner’s work included two important changes to the Blomstrand theory, the first was that Werner described the two different ion possibilities in terms of location in the coordination sphere
Coordination complex
–
Alfred Werner
Coordination complex
–
Cisplatin, PtCl 2 (NH 3) 2 A platinum atom with four
ligands
Coordination complex
–
Synthesis of copper(II)-tetraphenylporphyrin, a metal complex, from
tetraphenylporphyrin and
copper(II) acetate monohydrate.
44.
Ligand field theory
–
Ligand field theory describes the bonding, orbital arrangement, and other characteristics of coordination complexes. It represents an application of molecular orbital theory to transition metal complexes, a transition metal ion has nine valence atomic orbitals - consisting of five nd, three p, and one s orbitals. These orbitals are of appropriate energy to form bonding interaction with ligands, the LFT analysis is highly dependent on the geometry of the complex, but most explanations begin by describing octahedral complexes, where six ligands coordinate to the metal. Other complexes can be described by reference to field theory. Griffith and Orgel championed ligand field theory as an accurate description of such complexes. In their paper, they propose that the cause of color differences in transition metal complexes in solution is the incomplete d orbital subshells. That is, the d orbitals of transition metals participate in bonding. In an octahedral complex, the orbitals created by coordination can be seen as resulting from the donation of two electrons by each of six σ-donor ligands to the d-orbitals on the metal. In octahedral complexes, ligands approach along the x-, y- and z-axes, so their σ-symmetry orbitals form bonding and anti-bonding combinations with the dz2, the dxy, dxz and dyz orbitals remain non-bonding orbitals. The irreducible representations that these span are a1g, t1u and eg, the six σ-bonding molecular orbitals result from the combinations of ligand SALCs with metal orbitals of the same symmetry. π bonding in octahedral complexes occurs in two ways, via any ligand p-orbitals that are not being used in σ bonding, and via any π or π* molecular orbitals present on the ligand. In the usual analysis, the p-orbitals of the metal are used for σ bonding, so the π interactions take place with the appropriate metal d-orbitals, i. e. dxy, dxz and these are the orbitals that are non-bonding when only σ bonding takes place. One important π bonding in coordination complexes is metal-to-ligand π bonding and it occurs when the LUMOs of the ligand are anti-bonding π* orbitals. These orbitals are close in energy to the dxy, dxz and dyz orbitals, the ligands end up with electrons in their π* molecular orbital, so the corresponding π bond within the ligand weakens. The other form of coordination π bonding is ligand-to-metal bonding and this situation arises when the π-symmetry p or π orbitals on the ligands are filled. They combine with the dxy, dxz and dyz orbitals on the metal and it is filled with electrons from the metal d-orbitals, however, becoming the HOMO of the complex. For that reason, ΔO decreases when ligand-to-metal bonding occurs, the greater stabilization that results from metal-to-ligand bonding is caused by the donation of negative charge away from the metal ion, towards the ligands. This allows the metal to accept the σ bonds more easily, the combination of ligand-to-metal σ-bonding and metal-to-ligand π-bonding is a synergic effect, as each enhances the other
Ligand field theory
–
Ligand-Field scheme summarizing σ-bonding in the octahedral complex [Ti(H 2 O) 6] 3+.
45.
Pseudomorph
–
The name literally means false form. Terminology for pseudomorphs is replacer after original, as in brookite after rutile, an infiltration pseudomorph, or substitution pseudomorph is a pseudomorph in which one mineral or other material is replaced by another. The original shape of the mineral remains unchanged, but color, hardness, an example of this process is the replacement of wood by silica to form petrified wood in which the substitution may be so perfect as to retain the original cellular structure of the wood. An example of substitution is replacement of aragonite twin crystals by native copper, as occurs at the Corocoro United Copper Mines of Coro Coro. A variety of infiltration or substitution pseudomorphism is called alteration, in only partial replacement occurs. This happens typically when a mineral of one composition changes by chemical reaction to another of similar composition, an example is a change from galena to anglesite. The resulting pseudomorph may contain a core of galena surrounded by anglesite that has the cubic crystal shape of galena. A paramorph is a mineral changed on the level only. It has the chemical composition, but with a different structure. The mineral looks identical to the original unaltered form and this occurs, as an example, in the aragonite to calcite change. An incrustation pseudomorph, also called perimorph, results from a process by which a mineral is coated by another, the encasing mineral remains intact, and retains the shape of the original mineral or material. Alternatively, another mineral may fill the previously occupied by some other mineral or material. Pseudomorphs are also common in paleontology, fossils are often formed by pseudomorphic replacement of the remains by mineral matter. Examples include petrified wood and pyritized gastropod shells, in biology, a pseudomorph is a cloud of mucus-rich ink released by many species of cephalopod. The name refers to the similarity in appearance between the cephalopod that released it and the cloud itself, in context meaning literally false body. This behaviour often allows the cephalopod to escape from predation unharmed, danas Manual of Mineralogy by Cornelis S. Hurlbut, Eighteenth Edition, ISBN 0-471-42225-8 Polymorphism
Pseudomorph
–
Pseudomorph of
goethite after
pyrite
Pseudomorph
–
Native copper pseudomorph after
aragonite, with red
cuprite and green
malachite alteration
Pseudomorph
–
Iron oxides replacing
pyrite cubes
46.
Hans Holbein the Younger
–
Hans Holbein the Younger was a German and Swiss artist and printmaker who worked in a Northern Renaissance style. He is best known as one of the greatest portraitists of the 16th century and he also produced religious art, satire and Reformation propaganda, and made a significant contribution to the history of book design. He is called the Younger to distinguish him from his father, Hans Holbein the Elder, Born in Augsburg, Holbein worked mainly in Basel as a young artist. At first he painted murals and religious works and designed for stained glass windows and he also painted the occasional portrait, making his international mark with portraits of the humanist Desiderius Erasmus of Rotterdam. When the Reformation reached Basel, Holbein worked for reformist clients while continuing to serve traditional religious patrons and his Late Gothic style was enriched by artistic trends in Italy, France and the Netherlands, as well as by Renaissance humanism. The result was a combined aesthetic uniquely his own, Holbein travelled to England in 1526 in search of work, with a recommendation from Erasmus. He was welcomed into the humanist circle of Thomas More, where he built a high reputation. After returning to Basel for four years, he resumed his career in England in 1532 and this time he worked under the patronage of Anne Boleyn and Thomas Cromwell. By 1535, he was Kings Painter to King Henry VIII, in this role, he produced not only portraits and festive decorations but designs for jewellery, plate and other precious objects. His portraits of the family and nobles are a record of the court in the years when Henry was asserting his supremacy over the English church. Holbeins art was prized from early in his career, the French poet and reformer Nicholas Bourbon dubbed him the Apelles of our time, a typical contemporary accolade. Holbein has also described as a great one-off of art history. After his death, some of his work was lost, but much was collected, recent exhibitions have also highlighted his versatility. He turned his fluid line to designs ranging from jewellery to monumental frescoes. Holbeins art has sometimes been called realist, since he drew and his portraits were renowned in their time for their likeness, and it is through Holbeins eyes that many famous figures of his day, such as Erasmus and More, are now seen. Holbein was never content, however, with outward appearance and he embedded layers of symbolism, allusion, and paradox in his art, to the lasting fascination of scholars. In the view of art historian Ellis Waterhouse, his portraiture remains unsurpassed for sureness and economy of statement, penetration into character, Holbein was born in the free imperial city of Augsburg during the winter of 1497–98. He was a son of the painter and draughtsman Hans Holbein the Elder, whose trade he and his brother, Ambrosius
Hans Holbein the Younger
–
Hans Holbein the Younger
Hans Holbein the Younger
–
Hans (right) and
Ambrosius Holbein, by
Hans Holbein the Elder, 1511.
Silverpoint on white-coated paper,
Berlin State Museums
Hans Holbein the Younger
–
Portrait of
Erasmus of Rotterdam, 1523. Oil and
tempera on wood,
National Gallery, London, on loan from
Longford Castle
Hans Holbein the Younger
–
Portrait of Sir Thomas More, 1527. Oil and tempera on oak,
Frick Collection, New York City
47.
Pigment
–
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, many materials selectively absorb certain wavelengths of light. Materials that humans have chosen and developed for use as pigments usually have properties that make them ideal for coloring other materials. A pigment must have a high tinting strength relative to the materials it colors and it must be stable in solid form at ambient temperatures. For industrial applications, as well as in the arts, permanence, pigments that are not permanent are called fugitive. Fugitive pigments fade over time, or with exposure to light, pigments are used for coloring paint, ink, plastic, fabric, cosmetics, food, and other materials. Most pigments used in manufacturing and the arts are dry colorants. This powder is added to a binder, a neutral or colorless material that suspends the pigment. A distinction is made between a pigment, which is insoluble in its vehicle, and a dye, which either is itself a liquid or is soluble in its vehicle. A colorant can act as either a pigment or a dye depending on the vehicle involved, in some cases, a pigment can be manufactured from a dye by precipitating a soluble dye with a metallic salt. The resulting pigment is called a lake pigment, the term biological pigment is used for all colored substances independent of their solubility. In 2006, around 7.4 million tons of inorganic, organic, asia has the highest rate on a quantity basis followed by Europe and North America. By 2020, revenues will have risen to approx, the global demand on pigments was roughly US$20.5 billion in 2009, around 1. 5-2% up from the previous year. It is predicted to increase in a growth rate in the coming years. The worldwide sales are said to increase up to US$24.5 billion in 2015, pigments appear the colors they are because they selectively reflect and absorb certain wavelengths of visible light. White light is an equal mixture of the entire spectrum of visible light with a wavelength in a range from about 375 or 400 nanometers to about 760 or 780 nm. When this light encounters a pigment, parts of the spectrum are absorbed by the molecules or ions of the pigment, in organic pigments such as diazo or phthalocyanine compounds the light is absorbed by the conjugated systems of double bonds in the molecule. Some of the inorganic pigments such as vermilion or cadmium yellow absorb light by transferring an electron from the ion to the positive ion
Pigment
–
Natural
ultramarine pigment in powdered form
Pigment
–
Synthetic ultramarine pigment is chemically identical to natural ultramarine
Pigment
–
Miracle of the Slave by
Tintoretto (c. 1548). The son of a master
dyer, Tintoretto used Carmine Red Lake pigment, derived from the
cochineal insect, to achieve dramatic color effects.
Pigment
–
Girl with a Pearl Earring by
Johannes Vermeer (c. 1665).
48.
Fourth Dynasty of Egypt
–
The Fourth Dynasty of ancient Egypt is characterized as a golden age of the Old Kingdom. Dynasty IV lasted from c. 2613 to 2494 BC and it was a time of peace and prosperity as well as one during which trade with other countries is documented. Dynasties III, IV, V and VI are often combined under the title the Old Kingdom. The capital at time was Memphis. The Fourth Dynasty heralded the height of the pyramid-building age, the relative peace of the Third Dynasty allowed the Dynasty IV rulers the leisure to explore more artistic and cultural pursuits. Sneferu’s building experiments led to the evolution from the mastaba styled step pyramids to the smooth sided “true” pyramids, no other period in Egypt’s history equaled Dynasty IV’s architectural accomplishments. Each of the rulers of this dynasty commissioned at least one pyramid to serve as a tomb or cenotaph, the pharaohs of the Fourth Dynasty ruled for approximately 120 years, from c. 2613 to 2494 BC. The names in the table are taken from Dodson and Hilton and he also constructed a number of smaller step pyramids, making him the most prolific pyramid builder of the era. It is said that Sneferu had more stone and brick moved than any other pharaoh, sneferus chief wife was Hetepheres I, his half-sister and the mother of his son Khufu. His other two wives bore him more children, a well-liked ruler, Sneferu bolstered the power of the ruling family line by giving official titles and positions to relatives. He maintained control over the nobility by keeping a tight rein on lands and he conducted military excursions into Sinai, Nubia, Libya, and began trade arrangements with Lebanon for the acquisition of cedar. Surviving from this era are the records of Egyptian contact with her neighbors. They are recorded on the Palermo stone, information carved on the stone pre-dates and antedates this dynasty. Objects dating to the reign of Khafre have been found farther away, at Ebla. Khufu is the ruler who is known in Greek as Χέοψ = Cheops and his son is Khafre and his grandson is Menkaure. All of these rulers achieved lasting fame in the construction of their pyramids at Giza. In fact, recent excavations outside the Wall of the Crow by Dr. Mark Lehner have uncovered a city which seems to have housed, fed. Some records indicate that each household was responsible for providing a worker for civic projects, civic duties were not necessarily building projects, there were duties for the temples, libraries, and festivals as well, and both men and women filled some of the positions
Fourth Dynasty of Egypt
–
Statue of
Menkaura, flanked by
Hathor and
Bat to lend authority to the rule of the pharaoh
Fourth Dynasty of Egypt
–
Fragment of the
Palermo Stone which documents the arrival of ships during the reign of Sneferu - Petrie Museum, London
49.
Meidum
–
Meidum, Maydum or Maidum is an archaeological site in Lower Egypt. It contains a pyramid and several mud-brick mastabas. The area is located around 62 miles south of modern Cairo, the architect was a successor to the famous Imhotep, the inventor of the stone built pyramid. The collapse of the pyramid is likely due to the made to Imhoteps pyramid design as well as the decisions taken twice during construction to extend the pyramid. Because of its appearance, the pyramid is called el-heram el-kaddaab — in Egyptian Arabic. The second extension turned the original step pyramid design into a pyramid by filling in the steps with limestone encasing. While this approach is consistent with the design of the other true pyramids, firstly, the outer layer was founded on sand and not on rock, like the inner layers. Secondly, the step pyramids had been designed as the final stage. Thus the outer surface was polished and the platforms of the steps were not horizontal and this severely compromised the stability and is likely to have caused the collapse of the Meidum Pyramid in a downpour while the building was still under construction. Some believe the pyramid not to have collapsed until the New Kingdom, the Meidum Pyramid seems never to have been completed. Beginning with Sneferu and to the 12th dynasty all pyramids had a valley temple, the mortuary temple, which was found under the rubble at the base of the pyramid, apparently never was finished. Two Steles inside, usually bearing the names of the pharaoh, are missing inscriptions, the burial chamber inside the pyramid itself is uncompleted, with raw walls and wooden supports still in place which are usually removed after construction. Affiliated mastabas were never used or completed and none of the burials have been found. Finally, the first examinations of the Meidum Pyramid found everything below the surface of the rubble mound fully intact, stones from the outer cover were stolen only after they were exposed by the excavations. This makes a catastrophic collapse more probable than a gradual one, the collapse of this pyramid during the reign of Sneferu is the likely reason for the change from the usual 52 to 43 degrees of his second pyramid at Dahshur, the Bent Pyramid. By the time it was investigated by Napoleons Expedition in 1799 the Meidum Pyramid had its present three steps. The Meidum Pyramid was excavated by John Shae Perring in 1837, Lepsius in 1843 and then by Flinders Petrie later in the nineteenth century, in 1920 Ludwig Borchardt studied the area further, followed by Alan Rowe in 1928 and then Ali el-Kholi in the 1970s. In its ruined state, the structure is 213 feet high, the chamber is unlikely to have been used for any burial
Meidum
–
View of the Pyramid
Meidum
–
Lantern Slide Collection: Views, Objects: Egypt. Meidum. Old Kingdom. Step Pyramid of Meidum, 4th Dyn., n.d. Brooklyn Museum Archives
Meidum
–
Passageway in the Meidum Pyramid
Meidum
–
Another view of Meidum Pyramid
50.
Eighteenth Dynasty of Egypt
–
The eighteenth dynasty of ancient Egypt is the best known ancient Egyptian dynasty. It boasts several of Egypts most famous pharaohs, including Tutankhamun, the dynasty is also known as the Thutmosid Dynasty for the four pharaohs named Thutmosis. Famous pharaohs of Dynasty XVIII include Hatshepsut, longest-reigning woman-pharaoh of a dynasty, and Akhenaten. Dynasty XVIII is the first of the three dynasties of the Egyptian New Kingdom, the period in which ancient Egypt reached the peak of its power, radiocarbon dating suggests that Dynasty XVIII may have started a few years earlier than the conventional date of 1550 BC. The radiocarbon date range for its beginning is 1570–1544 BC, the point of which is 1557 BC. The pharaohs of Dynasty XVIII ruled for two hundred and fifty years. The dates and names in the table are taken from Dodson and Hilton, many of the pharaohs were buried in the Valley of the Kings in Thebes. More information can be found on the Theban Mapping Project website, several diplomatic marriages are known for the New Kingdom. These daughters of kings are often only mentioned in cuneiform texts and are not known from other sources. The marriages were likely a way to confirm good relations between these states, Dynasty XVIII was founded by Ahmose I, the brother or son of Kamose, the last ruler of the Dynasty XVII. Ahmose finished the campaign to expel the Hyksos rulers and his reign is seen as the end of the Second Intermediate Period and the start of the New Kingdom. Ahmose was succeeded by his son, Amenhotep I, whose reign was relatively uneventful, Amenhotep I probably left no male heir and the next pharaoh, Thutmose I, seems to have been related to the royal family through marriage. During his reign the borders of Egypts empire reached their greatest expanse, extending in the north to Carchemish on the Euphrates, Thutmose I was succeeded by Thutmose II and his queen, Hatshepsut. Thutmose III who later became known as the greatest military pharaoh ever and he had a second co-regency in his old age with his son Amenhotep II. Amenhotep II was succeeded by Thutmose IV, who in his turn was followed by his son Amenhotep III, the reign of Amenhotep III is seen as a high point in this dynasty. Amenhotep III undertook large scale building programmes, the extent of which can only be compared with those of the much longer reign of Ramesses II during Dynasty XIX. Amenhotep III may have shared the throne for up to twelve years with his son Amenhotep IV, there is much debate about this proposed co-regency. Some experts believe there was a lengthy co-regency, while others prefer to see a short one, there are also many experts who believe no such co-regency existed at all
Eighteenth Dynasty of Egypt
–
Head of an Early Eighteenth Dynasty King, ca. 1539-1493 B.C.,37.38E,
Brooklyn Museum
Eighteenth Dynasty of Egypt
–
Block Statue of Ay, ca. 1336-1327 B.C.E. 66.174.1,
Brooklyn Museum
Eighteenth Dynasty of Egypt
–
Ahmose-Nefertari.
Ahmose-Nefertari was the daughter of
Seqenenre Tao II, a 17th dynasty king who rose up against the
Hyksos. Her brother Ahmose, expelled the Hyksos, and she became queen of a united Egypt. She was deified after she died.
Eighteenth Dynasty of Egypt
–
Amenhotep I gained the throne after his two elder brothers had died. He was the son of Ahmose and Ahmose-Nefertari. He was succeeded by Thutmose I who married his daughter, Ahmose.
"Azurite". Encyclopædia Britannica. 3 (11th ed.). 1911. p. 86.
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