1.
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
2.
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
3.
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.
4.
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
5.
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
6.
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
7.
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.
8.
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
9.
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.
10.
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.
11.
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
12.
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
13.
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
14.
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)
15.
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
16.
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.
17.
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.
18.
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.
19.
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).
20.
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
21.
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
22.
Monoclinic crystal system
–
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 crystal system
–
An example of the monoclinic crystals,
orthoclase
23.
Botryoidal
–
A botryoidal texture or mineral habit is one in which the mineral has a globular external form resembling a bunch of grapes as derived from the Greek. This is a form for many minerals particularly hematite where it is the classically recognized shape. It is also a form of goethite, smithsonite, fluorite and malachite. Each sphere in a mineral is smaller than that of a reniform mineral. Botryoidal minerals form when many nearby nuclei, specks of sand, dust, layers of mineral material are deposited radially around the nuclei. As more material is deposited, the spheres grow larger and eventually overlap with those that are nearby and these nearby spheres are then fused together to form the botryoidal cluster
Botryoidal
–
Botryoidal hematite
24.
Stalagmite
–
A stalagmite is a type of rock formation that rises from the floor of a cave due to the accumulation of material deposited on the floor from ceiling drippings. Stalagmites may be composed of amberat, lava, minerals, mud, peat, pitch, sand, the corresponding formation hanging down from the ceiling of a cave is a stalactite. Mnemonics have been developed for which word refers to type of formation, one is that stalactite has a C for ceiling. The most common stalagmites are speleothems, which form in limestone caves. This stalagmite formation occurs only under certain pH conditions within the underground cavern and they form through deposition of calcium carbonate and other minerals, which is precipitated from mineralized water solutions. Limestone is the form of calcium carbonate rock, which is dissolved by water that contains carbon dioxide. If stalactites – the ceiling formations – grow long enough to connect with stalagmites on the floor, oils and dirt from human contact can also stain the formation and change its color permanently. Another type of stalagmite is formed in lava tubes while lava is still active inside, the mechanism of formation is similar to that of limestone stalagmites. A key difference with lava stalagmites is that once the lava has ceased flowing and this means if the stalagmite were to be broken it would never grow back. Stalagmites in lava tubes are rarer than their stalactite counterparts because during formation the dripping material falls onto still-moving lava floors that absorb or carry the material away, the generic term lavacicle has been applied to lava stalactites and stalagmites indiscriminately, and evolved from the word icicle. A common stalagmite found seasonally or year round in many caves is the ice stalagmite, commonly referred to as icicles, water seepage from the surface will penetrate into a cave and if temperatures are below freezing temperature, the water will collect on the floor into stalagmites. Deposition may also directly from the freezing of water vapor. Similar to lava stalagmites, ice stalagmites form very quickly within hours or days, unlike lava stalagmites however, they may grow back as long as water and temperatures are suitable. Ice stalagmites are more common than their stalactite counterparts because warmer air rises to the ceilings of caves, ice stalactites may also form corresponding stalagmites below them, and given time, may grow together to form an ice column. Stalactites and stalagmites can also form on concrete ceilings and floors, calcium carbonate deposition as a stalagmite occurs when the solution carries the calcium laden leachate solution to the ground under the concrete structure. Carbon dioxide is absorbed into the alkaline solution, which facilitates the chemical reactions to deposit calcium carbonate as a stalagmite. These stalagmites rarely grow taller than a few centimetres, secondary deposits, which create stalagmites, stalactites, flowstone etc, outside the natural cave environment, are referred to as “calthemites”. These concrete derived secondary deposits can’t be referred to as “speleothems” due to the definition of the word, the largest known stalagmite in the world exceeds 70 metres in height and is located in Sơn Đoòng Cave, Vietnam
Stalagmite
–
Image showing the six most common
speleothems with labels. Enlarge to view labels.
Stalagmite
–
The “Witch’s Finger” in the
Carlsbad Caverns, New Mexico
Stalagmite
–
Coves d’Artà, Mallorca, Spain
Stalagmite
–
Seven-Star Cave, Guilin, China
25.
Acicular (crystal habit)
–
Acicular, in mineralogy, refers to a crystal habit composed of slender, needle-like crystals. Crystals with this habit tend to be fragile, complete, undamaged acicular specimens are uncommon. The term acicular derives from the Late Latin acicula meaning little needle, strictly speaking, the word refers to a growth habit that is slender and tapering to a point. Prismatic crystals are not acicular, however, colloquial usage has altered the commonly understood meaning of the word, when writing for mineralogical publications, authors should restrict their usage of acicular to crystals with the tapering growth habit. To add to the confusion, some minerals are described with various morphological terms, for example, natrolite is often described as slender prismatic and millerite is often described as filiform or capillary. Minerals with an acicular habit include mesolite, natrolite, malachite, gypsum, rutile, crystals of dimethyltryptamine have an acicular habit, but this substance is not regarded as a mineral by the International Mineralogical Association
Acicular (crystal habit)
–
Natrolite showing acicular crystal habit
Acicular (crystal habit)
–
Needle-shaped acicular
millerite crystals on white
quartz
26.
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
27.
Azurite
–
Azurite is a soft, deep blue copper mineral produced by weathering of copper ore deposits. It is also known as Chessylite after the locality at Chessy-les-Mines near Lyon. The mineral, a carbonate, has known since ancient times, and was mentioned in Pliny the Elders Natural History under the Greek name kuanos. The blue of azurite is exceptionally deep and clear, and for that reason the mineral has tended to be associated since antiquity with the blue color of low-humidity desert. Azurite is one of the two basic copper carbonate minerals, the other being bright green malachite, simple copper carbonate is not known to exist in nature. Azurite has the formula Cu322, with the copper cations linked to two different anions, carbonate and hydroxide, small crystals of azurite can be produced by rapidly stirring a few drops of copper sulfate solution into a saturated solution of sodium carbonate and allowing the solution to stand overnight. Large crystals are blue, often prismatic. Azurite specimens can be massive to nodular and they are often stalactitic in form. Specimens tend to lighten in color over time due to weathering of the surface into malachite. Azurite is soft, with a Mohs hardness of only 3.5 to 4, the specific gravity of azurite is 3.77 to 3.89. Azurite is destroyed by heat, losing carbon dioxide and water to form black, characteristic of a carbonate, specimens effervesce upon treatment with hydrochloric acid. The optical properties of such as azurite and malachite are characteristic of copper. Many coordination complexes of copper exhibit similar colors, as explained within the context of ligand field theory, the colors result from low energy d-d transitions associated with the d9 metal center. Azurite is unstable in air with respect to malachite. Azurite is also incompatible with media, such as saltwater aquariums. Azurite is not a useful pigment because it is unstable in air and it was however used as a blue pigment in antiquity. Azurite is naturally occurring in Sinai and the Eastern Desert of Egypt and it was reported by F. C. J. Depending on the degree of fineness to which it was ground and it has been known as mountain blue or Armenian stone, in addition it was formerly known as Azurro Della Magna
Azurite
–
Azurite with large crystals and light surface weathering. Shilu Mine,
Guangdong Province, China
Azurite
–
Ground azurite for use as a pigment
Azurite
–
The background of Lady with a Squirrel by
Hans Holbein the Younger was painted with Azurite
Azurite
–
The greenish tint of the Madonna's mantle in Raphael Madonna and Child Enthroned with Saints is due to azurite weathering to malachite
28.
Neolithic era
–
It ended when metal tools became widespread. The Neolithic is a progression of behavioral and cultural characteristics and changes, including the use of wild and domestic crops, the beginning of the Neolithic culture is considered to be in the Levant about 10, 200–8800 BC. It developed directly from the Epipaleolithic Natufian culture in the region, whose people pioneered the use of wild cereals, which then evolved into true farming. The Natufian period was between 12,000 and 10,200 BC, and the so-called proto-Neolithic is now included in the Pre-Pottery Neolithic between 10,200 and 8800 BC. By 10, 200–8800 BC, farming communities arose in the Levant and spread to Asia Minor, North Africa, Mesopotamia is the site of the earliest developments of the Neolithic Revolution from around 10,000 BC. Early Neolithic farming was limited to a range of plants, both wild and domesticated, which included einkorn wheat, millet and spelt, and the keeping of dogs, sheep. By about 6900–6400 BC, it included domesticated cattle and pigs, the establishment of permanently or seasonally inhabited settlements, not all of these cultural elements characteristic of the Neolithic appeared everywhere in the same order, the earliest farming societies in the Near East did not use pottery. Early Japanese societies and other East Asian cultures used pottery before developing agriculture, unlike the Paleolithic, when more than one human species existed, only one human species reached the Neolithic. The term Neolithic derives from the Greek νέος néos, new and λίθος líthos, stone, the term was invented by Sir John Lubbock in 1865 as a refinement of the three-age system. In the Middle East, cultures identified as Neolithic began appearing in the 10th millennium BC, early development occurred in the Levant and from there spread eastwards and westwards. Neolithic cultures are attested in southeastern Anatolia and northern Mesopotamia by around 8000 BC. The total excavated area is more than 1,200 square yards, the Neolithic 1 period began roughly 10,000 years ago in the Levant. A temple area in southeastern Turkey at Göbekli Tepe dated around 9500 BC may be regarded as the beginning of the period. This site was developed by nomadic tribes, evidenced by the lack of permanent housing in the vicinity. At least seven stone circles, covering 25 acres, contain limestone pillars carved with animals, insects, Stone tools were used by perhaps as many as hundreds of people to create the pillars, which might have supported roofs. Other early PPNA sites dating to around 9500–9000 BC have been found in Jericho, Israel, Gilgal in the Jordan Valley, the start of Neolithic 1 overlaps the Tahunian and Heavy Neolithic periods to some degree. The major advance of Neolithic 1 was true farming, in the proto-Neolithic Natufian cultures, wild cereals were harvested, and perhaps early seed selection and re-seeding occurred. The grain was ground into flour, emmer wheat was domesticated, and animals were herded and domesticated
Neolithic era
–
An array of Neolithic artifacts, including bracelets, axe heads, chisels, and polishing tools. Neolithic stone artifacts are by definition polished and, except for specialty items, not chipped.
Neolithic era
–
Algerian cave paintings depicting hunting scenes
Neolithic era
–
Female figure from
Tumba Madžari,
Republic of Macedonia
Neolithic era
–
Skara Brae, Scotland. Evidence of home furnishings (shelves)
29.
Latin language
–
Latin is a classical language belonging to the Italic branch of the Indo-European languages. The Latin alphabet is derived from the Etruscan and Greek alphabets, Latin was originally spoken in Latium, in the Italian Peninsula. Through the power of the Roman Republic, it became the dominant language, Vulgar Latin developed into the Romance languages, such as Italian, Portuguese, Spanish, French, and Romanian. Latin, Italian and French have contributed many words to the English language, Latin and Ancient Greek roots are used in theology, biology, and medicine. By the late Roman Republic, Old Latin had been standardised into Classical Latin, Vulgar Latin was the colloquial form spoken during the same time and attested in inscriptions and the works of comic playwrights like Plautus and Terence. Late Latin is the language from the 3rd century. Later, Early Modern Latin and Modern Latin evolved, Latin was used as the language of international communication, scholarship, and science until well into the 18th century, when it began to be supplanted by vernaculars. Ecclesiastical Latin remains the language of the Holy See and the Roman Rite of the Catholic Church. Today, many students, scholars and members of the Catholic clergy speak Latin fluently and it is taught in primary, secondary and postsecondary educational institutions around the world. The language has been passed down through various forms, some inscriptions have been published in an internationally agreed, monumental, multivolume series, the Corpus Inscriptionum Latinarum. Authors and publishers vary, but the format is about the same, volumes detailing inscriptions with a critical apparatus stating the provenance, the reading and interpretation of these inscriptions is the subject matter of the field of epigraphy. The works of several hundred ancient authors who wrote in Latin have survived in whole or in part and they are in part the subject matter of the field of classics. The Cat in the Hat, and a book of fairy tales, additional resources include phrasebooks and resources for rendering everyday phrases and concepts into Latin, such as Meissners Latin Phrasebook. The Latin influence in English has been significant at all stages of its insular development. From the 16th to the 18th centuries, English writers cobbled together huge numbers of new words from Latin and Greek words, dubbed inkhorn terms, as if they had spilled from a pot of ink. Many of these words were used once by the author and then forgotten, many of the most common polysyllabic English words are of Latin origin through the medium of Old French. Romance words make respectively 59%, 20% and 14% of English, German and those figures can rise dramatically when only non-compound and non-derived words are included. Accordingly, Romance words make roughly 35% of the vocabulary of Dutch, Roman engineering had the same effect on scientific terminology as a whole
Latin language
–
Latin inscription, in the
Colosseum
Latin language
–
Julius Caesar 's
Commentarii de Bello Gallico is one of the most famous classical Latin texts of the Golden Age of Latin. The unvarnished, journalistic style of this
patrician general has long been taught as a model of the urbane Latin officially spoken and written in the floruit of the
Roman republic.
Latin language
–
A multi-volume Latin dictionary in the
University Library of Graz
Latin language
–
Latin and Ancient Greek Language - Culture - Linguistics at
Duke University in 2014.
30.
Middle English
–
This stage of the development of the English language roughly followed the High to the Late Middle Ages. Middle English developed out of Late Old English, seeing many dramatic changes in its grammar, pronunciation and this largely forms the basis for Modern English spelling, although pronunciation has changed considerably since that time. Middle English was succeeded in England by the era of Early Modern English, by that time, a variant of the Northumbrian dialect was developing into the Scots language. During the Middle English period many Old English grammatical features were simplified or disappeared, noun, adjective and verb inflections were simplified, a process that included the reduction of most grammatical case distinctions. Middle English also saw an adoption of Norman French vocabulary, especially in areas such as politics, law. Everyday English vocabulary remained mostly Germanic, with Old Norse influence becoming apparent, significant changes in pronunciation took place, especially for long vowels and diphthongs, which in the later Middle English period began to undergo the Great Vowel Shift. Little survives of early Middle English literature, most likely due to the Norman domination, poets wrote both in the vernacular and courtly English. It is popularly believed that William Shakespeare wrote in Middle English, the latter part of the 11th century was a period of transition from Late Old English to Early Middle English. The influence of Old Norse certainly helped move English from a synthetic language towards a more analytic or isolating word order and it was, after all, a salutary influence. The gain was greater than the loss, there was a gain in directness, in clarity, and in strength. The change to Old English from Old Norse was substantive, pervasive and it is most important to recognise that in many words the English and Scandinavian language differed chiefly in their inflectional elements. The body of the word was so nearly the same in the two languages only the endings would put obstacles in the way of mutual understanding. In the mixed population which existed in the Danelaw these endings must have led to confusion, tending gradually to become obscured. This blending of peoples and languages resulted in simplifying English grammar. There are also many Norman-derived terms relating to the cultures that arose in the 12th century. Sometimes, and particularly later, words were taken from Latin, giving such sets as kingly, later French borrowings came from standard rather than Norman French, this leads to such cognate pairs as warden, guardian. The end of Anglo-Saxon rule did not, of course, change the language immediately, the general population would have spoken the same dialects as before the Conquest, these changed slowly until written records of them became available for study, which varies in different regions. Once the writing of Old English came to an end, Middle English had no standard language, Early Middle English has a largely Anglo-Saxon vocabulary, but a greatly simplified inflectional system
Middle English
–
A page from
Geoffrey Chaucer 's
The Canterbury Tales
31.
Greek language
–
Greek is an independent branch of the Indo-European family of languages, native to Greece and other parts of the Eastern Mediterranean. It has the longest documented history of any living language, spanning 34 centuries of written records and its writing system has been the Greek alphabet for the major part of its history, other systems, such as Linear B and the Cypriot syllabary, were used previously. The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic and many other writing systems. Together with the Latin texts and traditions of the Roman world, during antiquity, Greek was a widely spoken lingua franca in the Mediterranean world and many places beyond. It would eventually become the official parlance of the Byzantine Empire, the language is spoken by at least 13.2 million people today in Greece, Cyprus, Italy, Albania, Turkey, and the Greek diaspora. Greek roots are used to coin new words for other languages, Greek. Greek has been spoken in the Balkan peninsula since around the 3rd millennium BC, the earliest written evidence is a Linear B clay tablet found in Messenia that dates to between 1450 and 1350 BC, making Greek the worlds oldest recorded living language. Among the Indo-European languages, its date of earliest written attestation is matched only by the now extinct Anatolian languages, the Greek language is conventionally divided into the following periods, Proto-Greek, the unrecorded but assumed last ancestor of all known varieties of Greek. The unity of Proto-Greek would have ended as Hellenic migrants entered the Greek peninsula sometime in the Neolithic era or the Bronze Age, Mycenaean Greek, the language of the Mycenaean civilisation. It is recorded in the Linear B script on tablets dating from the 15th century BC onwards, Ancient Greek, in its various dialects, the language of the Archaic and Classical periods of the ancient Greek civilisation. It was widely known throughout the Roman Empire, after the Roman conquest of Greece, an unofficial bilingualism of Greek and Latin was established in the city of Rome and Koine Greek became a first or second language in the Roman Empire. The origin of Christianity can also be traced through Koine Greek, Medieval Greek, also known as Byzantine Greek, the continuation of Koine Greek in Byzantine Greece, up to the demise of the Byzantine Empire in the 15th century. Much of the written Greek that was used as the language of the Byzantine Empire was an eclectic middle-ground variety based on the tradition of written Koine. Modern Greek, Stemming from Medieval Greek, Modern Greek usages can be traced in the Byzantine period and it is the language used by the modern Greeks, and, apart from Standard Modern Greek, there are several dialects of it. In the modern era, the Greek language entered a state of diglossia, the historical unity and continuing identity between the various stages of the Greek language is often emphasised. Greek speakers today still tend to regard literary works of ancient Greek as part of their own rather than a foreign language and it is also often stated that the historical changes have been relatively slight compared with some other languages. According to one estimation, Homeric Greek is probably closer to demotic than 12-century Middle English is to modern spoken English, Greek is spoken by about 13 million people, mainly in Greece, Albania and Cyprus, but also worldwide by the large Greek diaspora. Greek is the language of Greece, where it is spoken by almost the entire population
Greek language
–
Idealized portrayal of
Homer
Greek language
–
regions where Greek is the official language
Greek language
–
Greek language road sign, A27 Motorway, Greece
32.
Malva
–
The genus is widespread throughout the temperate, subtropical and tropical regions of Africa, Asia and Europe. The word mallow is derived from Old English malwe, which was imported from Latin malva, cognate with Ancient Greek μαλάχη meaning mallow, a number of species, previously considered to belong to Lavatera, have been moved to Malva. The leaves are alternate, palmately lobed, the flowers are from 0. 5–5 cm diameter, with five pink or white petals. The colour mauve was in 1859 named after the French name for this plant, several species are widely grown as garden flowers, while some are invasive weeds, particularly in the Americas where they are not native. Many species are edible as leaf vegetables and commonly foraged in the West, known as ebegümeci in Turkish, it is used as vegetable in Turkey in various forms such as stuffing the leaves with bulgur or rice or using the boiled leaves as side dish. Malva verticillata is grown on a commercial scale in China. Very easily grown, short-lived perennials are grown as ornamental plants. Mild tasting, young leaves can be a substitute for lettuce. The buds and flowers can be used in salads, cultivation is by sowing the seeds directly outdoors in early spring. The seed is easy to collect, and they will spread themselves by seed. In Catalonia they use the leaves to cure stinging nettles sting, bodos of Northeast India cultivate a sub-species of malva called lapha and use it extensively in their traditional cuisine, although its use is not much known among other people of India. Malva Leaves are a highly cherished vegetable dish in north Indian state of Kashmir, Malva sp. leaves have been used in the traditional Austrian medicine internally as tea or externally as baths for treatment of disorders of the skin, gastrointestinal tract and respiratory tract. This plant is one of the earliest cited in recorded literature, the third century BC physician Diphilus of Siphnus wrote that juice lubricates the windpipe, nourishes, and is easily digested. Horace mentions it in reference to his own diet, which he describes as simple, Me pascunt olivae. Sources, Data related to Malva at Wikispecies
Malva
–
Malva
Malva
–
Malva sylvestris
33.
Great Orme Mines
–
The Great Orme is a prominent limestone headland on the north coast of Wales, next to the town of Llandudno. It is referred to as Cyngreawdr Fynydd in a poem by the 12th-century poet Gwalchmai ap Meilyr and its English name derives from the Viking word for sea serpent, which it is said to resemble. It is echoed by the Little Orme, a smaller but very similar limestone headland on the side of Llandudno Bay in the parish of Llanrhos. Both the Great and Little Ormes have been linked to the Old Norse words urm or orm that mean sea serpent. The Great Orme being the head, with its body being the land between the Great and Little Ormes, still some Norse names remain in use within the former Kingdom of Gwynedd. Despite there being a theory for the origin of the name Orme, prior to this, Welsh names were predominantly used locally and in cartography to name the headlands landward features and the surrounding area. The entire peninsula on which Llandudno was built was known as the Creuddyn, Orme only appears to have been applied to the headland as seen from the sea. The first series Ordnance Survey map follows this convention, the headland is called the Great Ormes Head but its landward features all have Welsh names. It is likely that Orme became established as its name due to Llandudnos burgeoning tourist trade because a majority of visitors and holidaymakers regularly arrived by sea. The headland being the first thing to be sighted of their destination in the journey from Liverpool by paddle steamer. Parts of the Great Orme are managed as a reserve by the Conwy County Borough Countryside Service. The area, which is 2 miles long by 1 mile wide, has a number of protective designations including Special Area of Conservation, Heritage Coast, Country Park, the local authority provides a warden service on the Great Orme that reguarlly patrols the special scientific and conservation areas. There are numerous maintained paths for walking to the summit, a section of the long-distance North Wales Path also crosses the headland, about half the Great Orme is in use as farmland, mostly for sheep grazing. In 2015, the National Trust purchased the summits 140-acre Parc Farm for £1million, the Great Orme is a peninsula made mostly of limestone and dolomite, formed during the Early Carboniferous part of the Earths geological history. Most of the Great Ormes rocks are between 339 and 326 million years old, the upper surface of the Great Orme is particularly noted for its limestone pavements covering several headland areas. There are also rich seams of dolomite-hosted copper ore, the Great Orme copper mine was estimated to have produced enough copper to make about 2,000 tons of bronze during the Bronze Age. The slopes of the Great Orme are subject to occasional subsidence, natural wells were greatly prized in limestone districts and the Great Orme was no exception. Water was required for mining purposes as well as for domestic
Great Orme Mines
–
Great Orme panorama from
Llandudno promenade
Great Orme Mines
–
A view of the Great Orme's
limestone cliffs from the former
lighthouse
Great Orme Mines
–
Landscaped gardens in Happy Valley
Great Orme Mines
–
One of the Great Orme's Kashmiri goats grazing on its slopes
34.
Timna Valley
–
The Timna Valley is located in southern Israel in the southwestern Arabah, approximately 30 kilometres north of the Gulf of Aqaba and the town of Eilat. The area is rich in ore and has been mined since the 5th millennium BCE. There is controversy whether the mines were active during the Kingdom of Israel, a large section of the valley, containing ancient remnants of copper mining and ancient worship, is encompassed in a recreation park. In July 2011, the Israeli government approved the construction of an international airport, copper has been mined in the area since the 5th or 6th millennium BCE. The copper was used for ornaments, but more importantly for stone cutting, as saws, scientific attention and public interest was aroused in the 1930s, when Nelson Glueck attributed the copper mining at Timna to King Solomon and named the site King Solomons Mines. His excavation and restoration of the allowed for the reconstruction of Timna Valley’s long and complex history of copper production. The modern state of Israel also began mining copper on the edge of the valley in 1955. The mine was reopened in 1980, the mine was named Timnah after a Biblical chief. Timna Valley is notable for its uncommon stone formations and sand, although predominantly red, the sand can be yellow, orange, grey, dark brown, or black. Light green or blue sand occurs near the copper mines, water and wind erosion have created several unusual formations that are only found in similar climates. The most striking and well-known formation in Timna Valley are Solomons Pillars, the pillars are natural structures that were formed by centuries of water erosion through fractures in the sandstone cliff until it became a series of distinct, pillar-shaped structures. American archaeologist Nelson Glueck caused a surge of attention for the pillars in the 1930s and he claimed that the pillars were related to King Solomon and gave them the name Solomons Pillars. Although his hypothesis lacked support and has not been accepted, the name stuck, the pillars are known as the backdrop for evening concerts and dance performances the park presents in the summer. The Mushroom is a monolithic, mushroom-shaped, red sandstone rock formation known as a hoodoo. The mushroom shape was caused by wind, humidity, and water erosion over centuries, the Mushroom is surrounded by copper ore smelting sites from between the 14th and 12th centuries BCE. The Arches are natural arches formed by erosion, as well, Arches are not as rare as Solomons Pillars and the Mushroom, and similar structures can be found in elsewhere in the world. The walking trail goes to the Arches also goes past the copper mine shafts. Beno Rothenberg, the excavator of the Timna Valley area, excavated a small Egyptian temple dedicated to Hathor
Timna Valley
–
Sandstone cliffs in Timna Valley featuring King Solomon's Pillars.
Timna Valley
–
Chalcolithic copper mine in Timna Valley.
Timna Valley
–
Mine entrance.
Timna Valley
–
Mining tools.
35.
Ancient Egypt
–
Ancient Egypt was a civilization of ancient Northeastern Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. It is one of six civilizations to arise independently, Egyptian civilization followed prehistoric Egypt and coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh Narmer. In the aftermath of Alexander the Greats death, one of his generals, Ptolemy Soter and this Greek Ptolemaic Kingdom ruled Egypt until 30 BC, when, under Cleopatra, it fell to the Roman Empire and became a Roman province. The success of ancient Egyptian civilization came partly from its ability to adapt to the conditions of the Nile River valley for agriculture, the predictable flooding and controlled irrigation of the fertile valley produced surplus crops, which supported a more dense population, and social development and culture. Its art and architecture were widely copied, and its antiquities carried off to far corners of the world and its monumental ruins have inspired the imaginations of travelers and writers for centuries. The Nile has been the lifeline of its region for much of human history, nomadic modern human hunter-gatherers began living in the Nile valley through the end of the Middle Pleistocene some 120,000 years ago. By the late Paleolithic period, the climate of Northern Africa became increasingly hot and dry. In Predynastic and Early Dynastic times, the Egyptian climate was less arid than it is today. Large regions of Egypt were covered in treed savanna and traversed by herds of grazing ungulates, foliage and fauna were far more prolific in all environs and the Nile region supported large populations of waterfowl. Hunting would have been common for Egyptians, and this is also the period when many animals were first domesticated. The largest of these cultures in upper Egypt was the Badari, which probably originated in the Western Desert, it was known for its high quality ceramics, stone tools. The Badari was followed by the Amratian and Gerzeh cultures, which brought a number of technological improvements, as early as the Naqada I Period, predynastic Egyptians imported obsidian from Ethiopia, used to shape blades and other objects from flakes. In Naqada II times, early evidence exists of contact with the Near East, particularly Canaan, establishing a power center at Hierakonpolis, and later at Abydos, Naqada III leaders expanded their control of Egypt northwards along the Nile. They also traded with Nubia to the south, the oases of the desert to the west. Royal Nubian burials at Qustul produced artifacts bearing the oldest-known examples of Egyptian dynastic symbols, such as the crown of Egypt. They also developed a ceramic glaze known as faience, which was used well into the Roman Period to decorate cups, amulets, and figurines. During the last predynastic phase, the Naqada culture began using written symbols that eventually were developed into a system of hieroglyphs for writing the ancient Egyptian language. The Early Dynastic Period was approximately contemporary to the early Sumerian-Akkadian civilisation of Mesopotamia, the third-century BC Egyptian priest Manetho grouped the long line of pharaohs from Menes to his own time into 30 dynasties, a system still used today
Ancient Egypt
–
The
Great Sphinx and the
pyramids of Giza are among the most recognizable symbols of the civilization of ancient Egypt.
Ancient Egypt
–
A typical Naqada II jar decorated with gazelles. (Predynastic Period)
Ancient Egypt
–
The
Narmer Palette depicts the unification of the Two Lands.
36.
Acid
–
An acid is a molecule or ion capable of donating a hydron, or, alternatively, capable of forming a covalent bond with an electron pair. The first category of acids is the donors or Brønsted acids. In the special case of solutions, proton donors form the hydronium ion H3O+ and are known as Arrhenius acids. Brønsted and Lowry generalized the Arrhenius theory to include non-aqueous solvents, acids form aqueous solutions with a sour taste, can turn blue litmus red, and react with bases and certain metals to form salts. The word acid is derived from the Latin acidus/acēre meaning sour, an aqueous solution of an acid has a pH less than 7 and is colloquially also referred to as acid, while the strict definition refers only to the solute. A lower pH means a higher acidity, and thus a higher concentration of hydrogen ions in the solution. Chemicals or substances having the property of an acid are said to be acidic, common aqueous acids include hydrochloric acid, acetic acid, sulfuric acid, and citric acid. As these examples show, acids can be solutions or pure substances, strong acids and some concentrated weak acids are corrosive, but there are exceptions such as carboranes and boric acid. The second category of acids are Lewis acids, which form a covalent bond with an electron pair, however, hydrogen chloride, acetic acid, and most other Brønsted-Lowry acids cannot form a covalent bond with an electron pair and are therefore not Lewis acids. Conversely, many Lewis acids are not Arrhenius or Brønsted-Lowry acids, in modern terminology, an acid is implicitly a Brønsted acid and not a Lewis acid, since chemists almost always refer to a Lewis acid explicitly as a Lewis acid. Modern definitions are concerned with the chemical reactions common to all acids. Most acids encountered in life are aqueous solutions, or can be dissolved in water, so the Arrhenius. The Brønsted-Lowry definition is the most widely used definition, unless otherwise specified, hydronium ions are acids according to all three definitions. Interestingly, although alcohols and amines can be Brønsted-Lowry acids, they can function as Lewis bases due to the lone pairs of electrons on their oxygen and nitrogen atoms. The Swedish chemist Svante Arrhenius attributed the properties of acidity to hydrogen ions or protons in 1884, an Arrhenius acid is a substance that, when added to water, increases the concentration of H+ ions in the water. Thus, an Arrhenius acid can also be described as a substance that increases the concentration of ions when added to water. Examples include molecular substances such as HCl and acetic acid, an Arrhenius base, on the other hand, is a substance which increases the concentration of hydroxide ions when dissolved in water. Thus, an Arrhenius acid could also be said to be one that decreases hydroxide concentration, in an acidic solution, the concentration of hydronium ions is greater than 10−7 moles per liter
Acid
–
Zinc, a typical metal, reacting with
hydrochloric acid, a typical acid
Acid
–
Svante Arrhenius
Acid
–
Hydrochloric acid (in
beaker) reacting with
ammonia fumes to produce
ammonium chloride (white smoke).
37.
Malachite Room of the Winter Palace
–
It replaced the Jasper Room, which was destroyed in the fire of 1837. The room obtains its name from the use of malachite for its columns and this large salon contains a large malachite urn as well as furniture from the workshops of Peter Gambs, son of the famous furniture maker Heinrich Gambs, which were rescued from the 1837 fire. It was here that Romanov brides were traditionally dressed by the Tsarina before proceeding from the adjoining Arabian Hall to their weddings in the Grand Church, from June to October 1917 this room was the seat of the Russian Provisional Government. When the palace was stormed during the night of 7 November 1917, today, as part of the State Hermitage Museum, this room retains its original decoration. Citations Bibliography Media related to Category, Malachite Room in Winter Palace at Wikimedia Commons The Malachite Room today Flickr
Malachite Room of the Winter Palace
–
The Malachite Room, the Winter Palace, St Petersburg, by Konstantin Ukhtomsky (1865)
Malachite Room of the Winter Palace
Malachite Room of the Winter Palace
–
The Malachite Room, photographed c. 1900
Malachite Room of the Winter Palace
–
Location of the Malachite Room within the Winter Palace
38.
Hermitage Museum
–
The State Hermitage Museum is a museum of art and culture in Saint Petersburg, Russia. One of the largest and oldest museums in the world, it was founded in 1754 by Catherine the Great and has open to the public since 1852. Its collections, of only a small part is on permanent display. The collections occupy a complex of six historic buildings along Palace Embankment, including the Winter Palace. Apart from them, the Menshikov Palace, Museum of Porcelain, Storage Facility at Staraya Derevnya, the museum has several exhibition centers abroad. The Hermitage is a state property. Since July 1992, the director of the museum has been Mikhail Piotrovsky, of the six buildings in the main museum complex, five, namely the Winter Palace, Small Hermitage, Old Hermitage, New Hermitage and Hermitage Theatre, are open to the public. The entrance ticket for foreign tourists more than the fee paid by citizens of Russia. However, entrance is free of charge the first Thursday of every month for all visitors, the museum is closed on Mondays. The entrance for visitors is located in the Winter Palace. A hermitage is the dwelling of a hermit or recluse, the word derives from Old French hermit, ermit hermit, recluse, from Late Latin eremita, from Greek eremites, literally people who live alone, which is in turn derived from ἐρημός, desert. Originally, the building housing the collection was the Small Hermitage. Today, the Hermitage Museum encompasses many buildings on the Palace Embankment, apart from the Small Hermitage, the museum now also includes the Old Hermitage, the New Hermitage, the Hermitage Theatre, and the Winter Palace, the former main residence of the Russian tsars. In recent years, the Hermitage has expanded to the General Staff Building on the Palace Square facing the Winter Palace, the Western European Art collection includes European paintings, sculpture, and applied art from the 13th to the 20th centuries. It is displayed, in about 120 rooms, on the first, drawings and prints are displayed in temporary exhibitions. Since 1940, the Egyptian collection, dating back to 1852 and it serves as a passage to the exhibition of Classical Antiquities. A modest collection of the culture of Ancient Mesopotamia, including a number of Assyrian reliefs from Babylon, Dur-Sharrukin, the collection of Classical Antiquities occupies most of the ground floor of the Old and New Hermitage buildings. Its floor is made of a marble mosaic imitating ancient tradition, while the stucco walls
Hermitage Museum
–
Winter Palace
Hermitage Museum
–
The Hermitage Museum complex. From left to right: Hermitage Theatre – Old Hermitage – Small Hermitage – Winter Palace (the "New Hermitage" is situated behind the Old Hermitage).
Hermitage Museum
–
Egyptian Hall
Hermitage Museum
–
The Pavilion Hall
39.
Castillo de Chapultepec
–
Chapultepec Castle is located on top of Chapultepec Hill. The name Chapultepec stems from the Nahuatl word chapoltepēc which means at the grasshoppers hill and it is located in the middle of Chapultepec Park in Mexico City at a height of 2,325 meters above sea level. In 1775 Viceroy Bernardo de Gálvez ordered the construction of a home for himself at the highest point of Chapultepec Hill. Francisco Bambitelli, Lieutenant Colonel of the Spanish Army and engineer, drew up the blueprint, after Bambitellis departure to Havana, Captain Manuel Agustín Mascaró took over the leadership of the project and during his tenure the works proceeded at a rapid pace. Mascaró was accused of building a fortress with the intent of rebelling against the Spanish Crown from there, Bernardo, the viceroy, died suddenly on November 8,1786, fueling speculation that he was poisoned. No evidence has yet been found which supports this claim, lacking a head engineer, the Spanish Crown ordered that the building be auctioned at a price equivalent to one-fifth of the quantity thus far spent thereon. Alexander von Humboldt visited the site in 1803 and condemned the sale of the windows by the Royal Treasury as a way of raising funds for the Crown. The building was bought in 1806 by the municipal government of Mexico City. Chapultepec Castle was abandoned during the Mexican War of Independence and for years later. On September 13,1847, the Niños Héroes died defending the castle while it was taken by United States forces during the Battle of Chapultepec of the US invasion of Mexico and they are honored with a large mural on the ceiling above the main entrance to the castle. The United States Marine Corps honors the Battle of Chapultepec and the subsequent occupation of Mexico City through the first line of the Marines Hymn, From the Halls of Montezuma. Several new rooms were built on the floor of the palace during the tenure of President Miguel Miramón. Botanist Wilhelm Knechtel was in charge of creating the aerial located on the roof of the building. Additionally, the Emperor brought from Europe countless pieces of furniture, objets dart, at this time, the castle was still located on the outskirts of Mexico City. Maximilian ordered the construction of a boulevard, to connect the Imperial residence with the city centre. Following the reestablishment of the Republic in 1867 by President Benito Juárez, however, the observatory was only functional for five years until they decided to move it to the former residence of the Archbishop in Tacubaya. The reason was to allow the return of the Colegio Militar to the premises as well as transforming the building into the presidential residence, the palace underwent several structural changes from 1882 and during the presidency of Porfirio Díaz. The other Presidents who made the palace their official residence were Francisco I, madero, Venustiano Carranza, Álvaro Obregón, Plutarco Elías Calles, Emilio Portes Gil, Pascual Ortiz Rubio and Abelardo Rodríguez
Castillo de Chapultepec
–
View of Chapultepec Castle from the Northeast
Castillo de Chapultepec
–
Maximilian I of Mexico by
Winterhalter, 1864. This portrait hangs in the castle today
Castillo de Chapultepec
–
Inside the Chapultepec Castle
Castillo de Chapultepec
–
Garden view
40.
Mexico City
–
Mexico City, or City of Mexico, is the capital and most populous city of Mexico. As an alpha global city, Mexico City is one of the most important financial centers in the Americas and it is located in the Valley of Mexico, a large valley in the high plateaus at the center of Mexico, at an altitude of 2,240 metres. The city consists of sixteen municipalities, the 2009 estimated population for the city proper was approximately 8.84 million people, with a land area of 1,485 square kilometres. The Greater Mexico City has a domestic product of US$411 billion in 2011. The city was responsible for generating 15. 8% of Mexicos Gross Domestic Product, as a stand-alone country, in 2013, Mexico City would be the fifth-largest economy in Latin America—five times as large as Costa Ricas and about the same size as Perus. Mexico’s capital is both the oldest capital city in the Americas and one of two founded by Amerindians, the other being Quito. In 1524, the municipality of Mexico City was established, known as México Tenochtitlán, Mexico City served as the political, administrative and financial center of a major part of the Spanish colonial empire. After independence from Spain was achieved, the district was created in 1824. Ever since, the left-wing Party of the Democratic Revolution has controlled both of them, in recent years, the local government has passed a wave of liberal policies, such as abortion on request, a limited form of euthanasia, no-fault divorce, and same-sex marriage. On January 29,2016, it ceased to be called the Federal District and is now in transition to become the countrys 32nd federal entity, giving it a level of autonomy comparable to that of a state. Because of a clause in the Mexican Constitution, however, as the seat of the powers of the federation, it can never become a state, the city of Mexico-Tenochtitlan was founded by the Mexica people in 1325. According to legend, the Mexicas principal god, Huitzilopochtli indicated the site where they were to build their home by presenting an eagle perched on a cactus with a snake in its beak. Between 1325 and 1521, Tenochtitlan grew in size and strength, eventually dominating the other city-states around Lake Texcoco, when the Spaniards arrived, the Aztec Empire had reached much of Mesoamerica, touching both the Gulf of Mexico and the Pacific Ocean. After landing in Veracruz, Spanish explorer Hernán Cortés advanced upon Tenochtitlan with the aid of many of the native peoples. Cortés put Moctezuma under house arrest, hoping to rule through him, the Aztecs thought the Spaniards were permanently gone, and they elected a new king, Cuitláhuac, but he soon died, the next king was Cuauhtémoc. Cortés began a siege of Tenochtitlan in May 1521, for three months, the city suffered from the lack of food and water as well as the spread of smallpox brought by the Europeans. Cortés and his allies landed their forces in the south of the island, the Spaniards practically razed Tenochtitlan during the final siege of the conquest. Cortés first settled in Coyoacán, but decided to rebuild the Aztec site to erase all traces of the old order and he did not establish a territory under his own personal rule, but remained loyal to the Spanish crown
Mexico City
–
From above
Torre Latinoamericana,
Mexico City Metropolitan Cathedral,
Anillo Periférico,
World Trade Center Mexico City,
Angel of Independence,
Chapultepec Castle,
St. Regis Hotel Tower and
Torre Mayor, Skyline of
Paseo de la Reforma and
Palacio de Bellas Artes.
Mexico City
–
Tenochtitlan, the Aztec capital.
Mexico City
–
The ruins of the
Templo Mayor.
Mexico City
–
The
Mexico City Metropolitan Cathedral was built by the Spaniards over the ruins of the main Aztec temple.
41.
Tazza (cup)
–
A tazza is a wide but shallow saucer-like dish either mounted on a stem and foot or on a foot alone. The word has been adopted by archaeologists and connoisseurs for this type of vessel, used either for drinking, serving small items of food. Tazze are most commonly made in metal, glass, or ceramics, the Farnese Tazza is a 2nd-century BC cameo cup of Hellenistic Egypt in four-layered sardonyx agate. It is now in the Naples National Archaeological Museum, and is 20 cm wide, the shape and the name are sometimes adopted for reference to very large sculptured objects, especially ones used for fountains. The colossal tazza in the Linda Hall Library, Kansas City and it was presented by Czar Nicholas II to August Heckscher in 1910 and given to the Linda Hall Library in 1972 by Mrs. Helen Spencer. It stands as the point in the center of the Main Reading Room of the library. This article incorporates text from a now in the public domain, Chisholm, Hugh
Tazza (cup)
–
Venetian glass tazza, ca 1550–1600
V&A Museum, no. 1860-1855)
42.
Tsar Nicholas II
–
Nicholas II was the last Emperor of Russia, ruling from 1 November 1894 until his forced abdication on 15 March 1917. His reign saw the fall of the Russian Empire from being one of the foremost great powers of the world to economic, Soviet historiography portrayed Nicholas as a weak and incompetent leader, whose decisions led to military defeats and the deaths of millions of his subjects. The Anglo-Russian Entente, designed to counter German attempts to influence in the Middle East. Nicholas approved the Russian mobilisation on 30 July 1914, which led to Germany declaring war on Russia on 1 August 1914 and it is estimated that around 3,300,000 Russians were killed in World War I. Following the February Revolution of 1917, Nicholas abdicated on behalf of himself and his son, Nicholas, the recovered remains of the Imperial Family were finally re-interred in St. Petersburg, eighty years to the day on 17 July 1998. In 1981, Nicholas, his wife and their children were canonized as martyrs by the Russian Orthodox Church Outside Russia, located in New York City. On 15 August 2000 Nicholas and his family were canonized as passion bearers, Nicholas was born in the Alexander Palace in Saint Petersburg, Russian Empire, the eldest son of Emperor Alexander III and Empress Maria Feodorovna of Russia. He had five siblings, Alexander, George, Xenia, Michael. Nicholas often referred to his father nostalgically in letters after Alexanders death in 1894 and he was also very close to his mother, as revealed in their published letters to each other. His paternal grandparents were Emperor Alexander II and Empress Maria Alexandrovna of Russia and his maternal grandparents were King Christian IX and Queen Louise of Denmark. Nicholas was of primarily German and Danish descent, his last ethnically Russian ancestor being Grand Duchess Anna Petrovna, Nicholas was related to several monarchs in Europe. His mothers siblings included Kings Frederik VIII of Denmark and George I of Greece, Nicholas, his wife Alexandra, and Kaiser Wilhelm II of Germany were all first cousins of King George V of the United Kingdom. Nicholas was also a first cousin of both King Haakon VII and Queen Maud of Norway, as well as King Constantine I of Greece, Tsar Nicholas II was the first cousin-once-removed of Grand Duke Nicholas Nikolaevich. To distinguish between them the Grand Duke was often known within the Imperial family as Nikolasha and Nicholas the Tall, while the Tsar was Nicholas the Short. In his childhood, Nicholas, his parents and siblings made annual visits to the Danish royal palaces of Fredensborg and Bernstorff to visit his grandparents, the king and queen. The visits also served as family reunions, as his mothers siblings would come from the United Kingdom, Germany. It was there in 1883, that he had a flirtation with one of his English first cousins, in 1873, Nicholas also accompanied his parents and younger brother, two-year-old George, on a two-month, semi-official visit to England. In London, Nicholas and his family stayed at Marlborough House, as guests of his Uncle Bertie and Aunt Alix, the Prince and Princess of Wales, where he was spoiled by his uncle
Tsar Nicholas II
–
Tsar Nicholas II, in the uniform of a
Royal Navy Admiral of the Fleet, c. 1909
Tsar Nicholas II
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Tsar Nicholas II of Russia with his physically similar cousin,
King George V of the United Kingdom (right), in German military uniforms in Berlin before the war; 1913
Tsar Nicholas II
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Tsarevich Nicholas in Japan (1891)
Tsar Nicholas II
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Official engagement photograph of Nicholas II and Alexandra, April 1894
43.
Linda Hall Library
–
The Linda Hall Library is a privately endowed American library of science, engineering and technology located in Kansas City, Missouri, sitting majestically on a 14-acre urban arboretum. It is the largest independently funded public library of science, engineering and technology in North America, established in 1946 through the philanthropy of Linda and Herbert F. Hall, of the Hall-Bartlett Grain Co. the library has achieved global recognition and stature. The library is open to the public with individual researchers, academic institutions and companies from Kansas City, though not affiliated with its neighbor, the University of Missouri-Kansas City, many students and faculty from UMKC and other local colleges and universities utilize the library each day. The librarys William N. Deramus III Cosmology Theater shows images of the cosmos from the Hubble Space Telescope and these images are delivered via ViewSpace to the library with daily updates that provide the library with new content for visitors. The librarys collection numbers over 2 million items and it was initially established by the purchase of the 62,358 books and other items—assembled by John Adams before he became president—that had belonged to the American Academy of Arts and Sciences. In 1995, the Engineering Societies Library was transferred to Library, an equal in significance to the Academy collection. The librarys distinguished History of Science Collection contains more than 10,000 volumes, including first editions of many landmarks of science, some of the oldest books in the collection date back to the fifteenth century. Online Tycho Brahes 1632 Astronomicall Coniectur Georg Joachim Rheticuss Narratio Prima George Catlins North American Indian Portfolio Archives Georg Joachim Rheticus, nicolaus Copernicus, De revolutionibus orbium coelestium. Isaac Newton, Philosophiae naturalis principia mathematica, charles Darwin, On the Origin of Species. The 14-acre grounds surrounding the library are home to over 338 trees representing some 52 genera and 145 species, the arboretum and gardens are further embellished by beds of viburnum, tree peonies and Missouri native woodland plants. The National Wildlife Federation’s Backyard Wildlife Habitat Program has awarded a certificate of merit to the library for its efforts in preserving the habitat of the grounds
Linda Hall Library
–
Linda Hall Library Main Reading Room
44.
Ore
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An ore is a type of rock that contains sufficient minerals with important elements including metals that can be economically extracted from the rock. The ores are extracted from the earth through mining, they are refined to extract the valuable element. The grade or concentration of an ore mineral, or metal, as well as its form of occurrence, will directly affect the costs associated with mining the ore. The cost of extraction must thus be weighed against the value contained in the rock to determine what ore can be processed. Metal ores are generally oxides, sulfides, silicates, or native metals that are not commonly concentrated in the Earths crust, the ores must be processed to extract the metals of interest from the waste rock and from the ore minerals. Ore bodies are formed by a variety of geological processes, the process of ore formation is called ore genesis. An ore deposit is an accumulation of ore and this is distinct from a mineral resource as defined by the mineral resource classification criteria. An ore deposit is one occurrence of a particular ore type, Ore deposits are classified according to various criteria developed via the study of economic geology, or ore genesis. Stratiform arkose-hosted and shale-hosted copper, typified by the Zambian copperbelt and this identifies, early on, whether further investment in estimation and engineering studies is warranted and identifies key risks and areas for further work. This is because the distribution of ores is unequal and dislocated from locations of peak demand. Other, lesser, commodities do not have international clearing houses and benchmark prices and this generally makes determining the price of ores of this nature opaque and difficult. Such metals include lithium, niobium-tantalum, bismuth, antimony and rare earths, most of these commodities are also dominated by one or two major suppliers with >60% of the worlds reserves. The London Metal Exchange aims to add uranium to its list of metals on warrant, the World Bank reports that China was the top importer of ores and metals in 2005 followed by the USA and Japan. Economic geology Mineral resource classification Ore genesis Petrology Froth Flotation Extractive metallurgy DILL, the “chessboard” classification scheme of mineral deposits, Mineralogy and geology from aluminum to zirconium, Earth-Science Reviews, Volume 100, Issue 1-4, June 2010, Pages 1-420
Ore
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Manganese ore –
psilomelane (size: 6.7 × 5.8 × 5.1 cm)
Ore
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Iron ore (
Banded iron formation)
Ore
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Lead ore –
galena and
anglesite (size: 4.8 × 4.0 × 3.0 cm)
Ore
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Gold ore (size: 7.5 × 6.1 × 4.1 cm)
45.
Goethite
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Goethite, is an iron bearing hydroxide mineral of the diaspore group, is found in soil and other low-temperature environments. Goethite has been known since ancient times for its use as a pigment. Evidence has been found of its use in paint pigment samples taken from the caves of Lascaux in France and it was first described in 1806 based on samples found in the Hollertszug Mine in Herdorf, Germany. The mineral was named after the German polymath and poet Johann Wolfgang von Goethe, in 2003, nanoparticulate authigenic goethite was shown to be the most common diagenetic iron oxyhydroxide in both marine and lake sediments. Goethite is an iron oxyhydroxide containing ferric iron and it is the main component of rust and bog iron ore. Goethites hardness ranges from 5.0 to 5.5 on the Mohs Scale, the mineral forms prismatic needle-like crystals, but is more typically massive. Feroxyhyte and lepidocrocite are both polymorphs of the iron oxyhydroxide FeO, although they have the same chemical formula as goethite, their different crystalline structures make them distinct minerals. Goethite often forms through the weathering of other minerals, and thus is a common component of soils. The formation of goethite is marked by the state change of Fe2+ to Fe3+. Because of this state change, goethite is commonly seen as a pseudomorph. As iron-bearing minerals are brought to the zone of oxidation within the soil and it may also be precipitated by groundwater or in other sedimentary conditions, or form as a primary mineral in hydrothermal deposits. Goethite has also found to be produced by the excretion processes of certain bacteria types. Goethite is found all over the planet, usually in the form of concretions, stalactitic formations, oolites and it is also a very common pseudomorph. It is frequently encountered in the areas at the head of spring waters, on cave floors. The boxworks or gossan resulting from the oxidation of ore deposits is formed of goethite along with other iron oxides. Significant deposits of goethite are found in England, Australia, Cuba, and Michigan, Minnesota, Missouri, Colorado, Alabama, Georgia, Virginia, and Tennessee, and Florida caves in the United States. In 2015 it was reported that limpets teeth have goethite fibres in them and its main modern use is as an iron ore, being referred to as brown iron ore. It does have some use as an earth pigment
Goethite
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Goethite, Restormel Royal Iron Mine, Cornwall, England.
Goethite
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Unusual specimen of Goethite replacing a
gypsum stalactite; the center is hollow. From
Santa Eulalia, Chihuahua, Mexico.
Goethite
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Goethite coating/replacing rusted
pyrite cubes.
46.
Calcite
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Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate. The Mohs scale of hardness, based on scratch hardness comparison. Other polymorphs of calcium carbonate are the minerals aragonite and vaterite, aragonite will change to calcite at 380–470 °C, and vaterite is even less stable. Calcite is derived from the German Calcit, a term coined in the 19th century from the Latin word for lime and it is thus etymologically related to chalk. Calcite crystals are trigonal-rhombohedral, though actual calcite rhombohedra are rare as natural crystals, however, they show a remarkable variety of habits including acute to obtuse rhombohedra, tabular forms, prisms, or various scalenohedra. Calcite exhibits several twinning types adding to the variety of observed forms and it may occur as fibrous, granular, lamellar, or compact. Cleavage is usually in three directions parallel to the rhombohedron form and its fracture is conchoidal, but difficult to obtain. It has a defining Mohs hardness of 3, a gravity of 2.71. Color is white or none, though shades of gray, red, orange, yellow, green, blue, violet, brown, calcite is transparent to opaque and may occasionally show phosphorescence or fluorescence. A transparent variety called Iceland spar is used for optical purposes, acute scalenohedral crystals are sometimes referred to as dogtooth spar while the rhombohedral form is sometimes referred to as nailhead spar. Single calcite crystals display an optical property called birefringence and this strong birefringence causes objects viewed through a clear piece of calcite to appear doubled. The birefringent effect was first described by the Danish scientist Rasmus Bartholin in 1669, at a wavelength of ~590 nm calcite has ordinary and extraordinary refractive indices of 1.658 and 1.486, respectively. Between 190 and 1700 nm, the refractive index varies roughly between 1.9 and 1.5, while the extraordinary refractive index varies between 1.6 and 1.4. Calcite, like most carbonates, will dissolve with most forms of acid, calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature, pH, and dissolved ion concentrations. Although calcite is fairly insoluble in water, acidity can cause dissolution of calcite. Ambient carbon dioxide, due to its acidity, has a slight solubilizing effect on calcite, calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases. When conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together or it can fill fractures. On a landscape scale, continued dissolution of calcium carbonate-rich rocks can lead to the expansion and eventual collapse of cave systems, high-grade optical calcite was used in World War II for gun sights, specifically in bomb sights and anti-aircraft weaponry
Calcite
–
A one-inch calcite
rhomb that shows the
double image refraction property
Calcite
–
Crystal structure of calcite
Calcite
–
faceted calcite, oval cut, 1.12ct, Mexico.
Calcite
–
Doubly terminated calcite crystal.
47.
Limestone
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Limestone is a sedimentary rock, composed mainly of skeletal fragments of marine organisms such as coral, forams and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate, about 10% of sedimentary rocks are limestones. The solubility of limestone in water and weak acid solutions leads to karst landscapes, most cave systems are through limestone bedrock. The first geologist to distinguish limestone from dolomite was Belsazar Hacquet in 1778, like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of organisms such as coral or foraminifera. Other carbonate grains comprising limestones are ooids, peloids, intraclasts and these organisms secrete shells made of aragonite or calcite, and leave these shells behind when they die. Limestone often contains variable amounts of silica in the form of chert or siliceous skeletal fragment, some limestones do not consist of grains at all, and are formed completely by the chemical precipitation of calcite or aragonite, i. e. travertine. Secondary calcite may be deposited by supersaturated meteoric waters and this produces speleothems, such as stalagmites and stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular appearance, the primary source of the calcite in limestone is most commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone typically does not form in deeper waters. Limestones may also form in lacustrine and evaporite depositional environments, calcite can be dissolved or precipitated by groundwater, depending on several factors, including the water temperature, pH, and dissolved ion concentrations. Calcite exhibits a characteristic called retrograde solubility, in which it becomes less soluble in water as the temperature increases. Impurities will cause limestones to exhibit different colors, especially with weathered surfaces, Limestone may be crystalline, clastic, granular, or massive, depending on the method of formation. Crystals of calcite, quartz, dolomite or barite may line small cavities in the rock, when conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together, or it can fill fractures. Travertine is a banded, compact variety of limestone formed along streams, particularly there are waterfalls. Calcium carbonate is deposited where evaporation of the leaves a solution supersaturated with the chemical constituents of calcite. Tufa, a porous or cellular variety of travertine, is found near waterfalls, coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism that occurs during the building process, limestone recrystallizes into marble
Limestone
–
Limestone outcrop in the
Torcal de Antequera nature reserve of
Málaga, Spain
Limestone
–
Limestone quarry at
Cedar Creek, Virginia, USA
Limestone
–
Cutting the limestone blocks at a quarry in
Gozo,
Malta
Limestone
–
Limestone as building material
48.
Urals
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The mountain range forms part of the conventional boundary between the continents of Europe and Asia. Vaygach Island and the islands of Novaya Zemlya form a continuation of the chain to the north into the Arctic Ocean. The mountains lie within the Ural geographical region and significantly overlap with the Ural Federal District and they have rich resources, including metal ores, coal, precious and semi-precious stones. Since the 18th century the mountains have contributed significantly to the sector of the Russian economy. As attested by Sigismund von Herberstein, in the 16th century Russians called the range by a variety of names derived from the Russian words for rock and it might have been a borrowing from either Turkic stone belt, or Ob-Ugric. From the 13th century, in Bashkortostan there has been a legend about a hero named Ural and he sacrificed his life for the sake of his people and they poured a stone pile over his grave, which later turned into the Ural Mountains. Possibilities include Bashkir үр elevation, upland or Mansi ур ала mountain peak, top of the mountain, tatischev believes that this oronym is set to belt and associates it with the Turkic verb oralu- gird. Dobrodomov suggests a transition from Aral to Ural explained on the basis of ancient Bulgar-Chuvash dialects, hawks believes that the name goes back to the Bashkir folklore Ural-Batyr. Shumilov suggested a Mongolian origin, Khural Uul, that is, the Evenk geographical term era mountain has also been theorized. Finno-Ugrist scholars consider Ural deriving from the Mansi word urr meaning a mountain, turkologists, on the other hand, have achieved majority support for their assertion that ural in Tatar means a belt, and recall that an earlier name for the range was stone belt. During the next few centuries Novgorodians engaged in fur trading with the population and collected tribute from Yugra and Great Perm. The rivers Chusovaya and Belaya were first mentioned in the chronicles of 1396 and 1468, in 1430 the town of Solikamsk was founded on the Kama at the foothills of the Ural, where salt was produced in open pans. Ivan III of Moscow captured Perm, Pechora and Yugra from the declining Novgorod Republic in 1472, with the excursions of 1483 and 1499–1500 across the Ural Moscow managed to subjugate Yugra completely. The Middle and Southern Ural were still largely unavailable and unknown to the Russian or Western European geographers, the Stroganovs land provided the staging ground for Yermaks incursion into Siberia. Yermak crossed the Ural from the Chusovaya to the Tagil around 1581, in 1597 Babinovs road was built across the Ural from Solikamsk to the valley of the Tura, where the town of Verkhoturye was founded in 1598. Customs was established in Verkhoturye shortly thereafter and the road was made the legal connection between European Russia and Siberia for a long time. In 1648 the town of Kungur was founded at the foothills of the Middle Ural. During the 17th century the first deposits of iron and copper ores, mica, gemstones, iron and copper smelting works emerged
Urals
–
Verkhoturye in 1910
Urals
Urals
–
Yugyd Va National Park
Urals
–
Mountain formation near Saranpaul, Nether-Polar Urals
49.
Russia
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Russia, also officially the Russian Federation, is a country in Eurasia. The European western part of the country is more populated and urbanised than the eastern. Russias capital Moscow is one of the largest cities in the world, other urban centers include Saint Petersburg, Novosibirsk, Yekaterinburg, Nizhny Novgorod. Extending across the entirety of Northern Asia and much of Eastern Europe, Russia spans eleven time zones and incorporates a range of environments. It shares maritime borders with Japan by the Sea of Okhotsk, the East Slavs emerged as a recognizable group in Europe between the 3rd and 8th centuries AD. Founded and ruled by a Varangian warrior elite and their descendants, in 988 it adopted Orthodox Christianity from the Byzantine Empire, beginning the synthesis of Byzantine and Slavic cultures that defined Russian culture for the next millennium. Rus ultimately disintegrated into a number of states, most of the Rus lands were overrun by the Mongol invasion. The Soviet Union played a role in the Allied victory in World War II. The Soviet era saw some of the most significant technological achievements of the 20th century, including the worlds first human-made satellite and the launching of the first humans in space. By the end of 1990, the Soviet Union had the second largest economy, largest standing military in the world. It is governed as a federal semi-presidential republic, the Russian economy ranks as the twelfth largest by nominal GDP and sixth largest by purchasing power parity in 2015. Russias extensive mineral and energy resources are the largest such reserves in the world, making it one of the producers of oil. The country is one of the five recognized nuclear weapons states and possesses the largest stockpile of weapons of mass destruction, Russia is a great power as well as a regional power and has been characterised as a potential superpower. The name Russia is derived from Rus, a state populated mostly by the East Slavs. However, this name became more prominent in the later history, and the country typically was called by its inhabitants Русская Земля. In order to distinguish this state from other states derived from it, it is denoted as Kievan Rus by modern historiography, an old Latin version of the name Rus was Ruthenia, mostly applied to the western and southern regions of Rus that were adjacent to Catholic Europe. The current name of the country, Россия, comes from the Byzantine Greek designation of the Kievan Rus, the standard way to refer to citizens of Russia is Russians in English and rossiyane in Russian. There are two Russian words which are translated into English as Russians
Russia
–
Kievan Rus' in the 11th century
Russia
–
Flag
Russia
–
The
Baptism of Kievans, by
Klavdy Lebedev
Russia
–
Sergius of Radonezh blessing
Dmitry Donskoy in
Trinity Sergius Lavra, before the
Battle of Kulikovo, depicted in a painting by
Ernst Lissner
50.
Democratic Republic of the Congo
–
The Democratic Republic of the Congo, also known as DR Congo, DRC, DROC, East Congo, Congo-Kinshasa, or simply the Congo is a country located in Central Africa. From 1971 to 1997 it was named, and is still called, Zaire. It is the second-largest country in Africa by area and eleventh largest in the world, the Congolese Civil Wars, which began in 1996, brought about the end of Mobutu Sese Sekos 32-year reign and devastated the country. These wars ultimately involved nine African nations, multiple groups of UN peacekeepers and twenty armed groups, besides the capital, Kinshasa, the other major cities, Lubumbashi and Mbuji-Mayi, are both mining communities. DR Congos largest export is raw minerals, with China accepting over 50% of DRCs exports in 2012, as of 2015, according to the Human Development Index, DR Congo has a low level of human development, ranking 176 out of 187 countries. The country was known officially as the Democratic Republic of the Congo from 1965 to 27 October 1971, in 1992, the Sovereign National Conference voted to change the name of the country to the Democratic Republic of the Congo, but the change was not put into practice. The countrys name was restored by former president Laurent-Désiré Kabila following the fall of longtime dictator Mobutu Sese Seko in 1997, some historians think that Bantu peoples began settling in the extreme northwest of Central Africa at the beginning of the 5th century and then gradually started to expand southward. Their propagation was accelerated by the transition from Stone Age to Iron Age techniques, the people living in the south and southwest were mostly San Bushmen and hunter-gatherer groups, whose technology involved only minimal use of metal technologies. The development of tools during this time period revolutionized agriculture. This led to the displacement of the groups in the east and southeast. The 10th century marked the expansion of the Bantu in West-Central Africa. Rising populations soon made intricate local, regional and foreign commercial networks that traded mostly in salt, iron. Belgian exploration and administration took place from the 1870s until the 1920s and it was first led by Sir Henry Morton Stanley, who undertook his explorations under the sponsorship of King Leopold II of Belgium. The eastern regions of the precolonial Congo were heavily disrupted by constant slave raiding, mainly from Arab–Swahili slave traders such as the infamous Tippu Tip, Leopold had designs on what was to become the Congo as a colony. Leopold formally acquired rights to the Congo territory at the Conference of Berlin in 1885 and he named it the Congo Free State. Leopolds rėgime began various infrastructure projects, such as construction of the railway ran from the coast to the capital of Leopoldville. Nearly all such projects were aimed at making it easier to increase the assets which Leopold. In the Free State, colonists brutalized the local population into producing rubber, for which the spread of automobiles, rubber sales made a fortune for Leopold, who built several buildings in Brussels and Ostend to honor himself and his country
Democratic Republic of the Congo
–
Village attacked by Arab-Swahili slavers near
Nyangwe, end of 19th century
Democratic Republic of the Congo
–
Flag
Democratic Republic of the Congo
–
View of
Leopoldville Station and Port in 1884.
Democratic Republic of the Congo
–
Force Publique soldiers in the Belgian Congo in 1918. At its peak, the Force Publique had around 19,000 African soldiers, led by 420 white officers.
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