1.
Sulfate minerals
–
The sulfate minerals are a class of minerals which include the sulfate ion within their structure. The chromate and manganate minerals have a structure and are often included with the sulfates in mineral classification systems. This list uses it to modify the Classification of Nickel–Strunz
Sulfate minerals
–
Barite with
cerussite
Sulfate minerals
–
Anhydrite crystal structure
Sulfate minerals
–
Hanksite, one of the rare minerals that is a sulfate and carbonate
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 structure
–
In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the nature of the constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter. The smallest group of particles in the material that constitutes the pattern is the unit cell of the structure. The unit cell completely defines the symmetry and structure of the crystal lattice. The repeating patterns are said to be located at the points of the Bravais lattice, the lengths of the principal axes, or edges, of the unit cell and the angles between them are the lattice constants, also called lattice parameters. The symmetry properties of the crystal are described by the concept of space groups, all possible symmetric arrangements of particles in three-dimensional space may be described by the 230 space groups. The crystal structure and symmetry play a role in determining many physical properties, such as cleavage, electronic band structure. The crystal structure of a material can be described in terms of its unit cell, the unit cell is a box containing one or more atoms arranged in three dimensions. The unit cells stacked in three-dimensional space describe the arrangement of atoms of the crystal. Commonly, atomic positions are represented in terms of fractional coordinates, the atom positions within the unit cell can be calculated through application of symmetry operations to the asymmetric unit. The asymmetric unit refers to the smallest possible occupation of space within the unit cell and this does not, however imply that the entirety of the asymmetric unit must lie within the boundaries of the unit cell. Symmetric transformations of atom positions are calculated from the group of the crystal structure. Vectors and planes in a lattice are described by the three-value Miller index notation. It uses the indices ℓ, m, and n as directional parameters, which are separated by 90°, by definition, the syntax denotes a plane that intercepts the three points a1/ℓ, a2/m, and a3/n, or some multiple thereof. That is, the Miller indices are proportional to the inverses of the intercepts of the plane with the unit cell, if one or more of the indices is zero, it means that the planes do not intersect that axis. A plane containing a coordinate axis is translated so that it no longer contains that axis before its Miller indices are determined, the Miller indices for a plane are integers with no common factors. Negative indices are indicated with horizontal bars, as in, in an orthogonal coordinate system for a cubic cell, the Miller indices of a plane are the Cartesian components of a vector normal to the plane. Likewise, the planes are geometric planes linking nodes
Crystal structure
–
Quartz is one of the several thermodynamically stable
crystalline forms of
silica, SiO 2. The most important forms of silica include:
α-quartz,
β-quartz,
tridymite,
cristobalite,
coesite, and
stishovite.
Crystal structure
9.
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
10.
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.
11.
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.
12.
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
13.
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
14.
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
15.
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)
16.
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
17.
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.
18.
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.
19.
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.
20.
Pleochroism
–
Pleochroism is an optical phenomenon in which a substance appears to be different colors when observed at different angles, especially with polarized light. Anisotropic crystals will have properties that vary with the direction of light. The polarization of light determines the direction of the electric field and these kinds of crystals have one or two optical axes. If absorption of light varies with the relative to the optical axis in a crystal then pleochroism results. Anisotropic crystals have double refraction of light where light of different polarizations is bent different amounts by the crystal, the components of a divided light beam follow different paths within the mineral and travel at different speeds. When the mineral is observed at some angle, light following some combination of paths and polarizations will be present, at another angle, the light passing through the crystal will be composed of another combination of light paths and polarizations, each with their own color. The light passing through the mineral will therefore have different colors when it is viewed from different angles, tetragonal, trigonal and hexagonal minerals can only show two colors and are called dichroic. Orthorhombic, monoclinic and triclinic crystals can show three and are trichroic, for example, hypersthene, with two optical axes, can have red, yellow or blue appearance when oriented in three different ways in three-dimensional space. Tourmaline is notable for exhibiting strong pleochroism, gems are sometimes cut and set either to display pleochroism or to hide it, depending on the colors and their attractiveness. The pleochroic colours are at their maximum when light is polarized parallel with a crystallographic axis, the axes are designated X, Y and Z. These axes can be determined from the appearance of a crystal in an interference pattern. Where there are two axes, the acute bisection of the axes gives Z for positive minerals and X for negative minerals. Perpendicular to these is the Y axis, the colour is measured with the polarization parallel to each direction. An absorption formula records the amount of parallel to each axis in the form of X < Y < Z with the left most having the least absorption. Minerals that are very similar often have very different pleochroic color schemes. In such cases, a section of the mineral is used and examined under polarized transmitted light with a petrographic microscope. Another device using this property to identify minerals is the dichroscope
Pleochroism
–
Cordierite
Pleochroism
–
Tourmaline
21.
Solubility
–
Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent. The solubility of a substance depends on the physical and chemical properties of the solute and solvent as well as on temperature, pressure. The solubility of a substance is a different property from the rate of solution. Most often, the solvent is a liquid, which can be a substance or a mixture. One may also speak of solid solution, but rarely of solution in a gas, the extent of solubility ranges widely, from infinitely soluble such as ethanol in water, to poorly soluble, such as silver chloride in water. The term insoluble is often applied to poorly or very poorly soluble compounds, a common threshold to describe something as insoluble is less than 0.1 g per 100 mL of solvent. Under certain conditions, the solubility can be exceeded to give a so-called supersaturated solution. Metastability of crystals can also lead to apparent differences in the amount of a chemical that dissolves depending on its form or particle size. A supersaturated solution generally crystallises when seed crystals are introduced and rapid equilibration occurs, phenylsalicylate is one such simple observable substance when fully melted and then cooled below its fusion point. Solubility is not to be confused with the ability to dissolve a substance, for example, zinc dissolves in hydrochloric acid as a result of a chemical reaction releasing hydrogen gas in a displacement reaction. The zinc ions are soluble in the acid, the smaller a particle is, the faster it dissolves although there are many factors to add to this generalization. Crucially solubility applies to all areas of chemistry, geochemistry, inorganic, physical, organic, in all cases it will depend on the physical conditions and the enthalpy and entropy directly relating to the solvents and solutes concerned. By far the most common solvent in chemistry is water which is a solvent for most ionic compounds as well as a range of organic substances. This is a factor in acidity/alkalinity and much environmental and geochemical work. According to the IUPAC definition, solubility is the composition of a saturated solution expressed as a proportion of a designated solute in a designated solvent. Solubility may be stated in units of concentration such as molarity, molality, mole fraction, mole ratio, mass per volume. Solubility occurs under dynamic equilibrium, which means that solubility results from the simultaneous and opposing processes of dissolution, the solubility equilibrium occurs when the two processes proceed at a constant rate. The term solubility is used in some fields where the solute is altered by solvolysis
Solubility
–
Diving medicine:
Solubility
–
"Soluble" redirects here. For the algebraic object called a "soluble group", see
Solvable group.
22.
Selenite (mineral)
–
Selenite, satin spar, desert rose, and gypsum flower are four varieties of the mineral gypsum, all four varieties show obvious crystalline structure. The four crystalline varieties of gypsum are sometimes grouped together and called selenite, all varieties of gypsum, including selenite and alabaster, are composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. Selenite contains no significant selenium, the similarity of names comes from both substances being named from the Ancient Greek word for the Moon. The etymology of selenite is through Middle English selinete, from Latin selenites, from Greek selēnitēs, literally, moonstone or stone of the moon, the ancients had a belief that certain transparent crystals waxed and waned with the moon. From the 15th century, selenite has referred specifically to the variety of gypsum that occurs in transparent crystals or crystalline masses, all varieties of gypsum are very soft minerals. This is the most important identifying characteristic of gypsum, as any variety of gypsum can be scratched with a fingernail. Also, because gypsum has natural thermal insulating properties, all varieties feel warm to the touch, though sometimes grouped together as selenite, the four crystalline varieties have differences. General identifying descriptions of the related crystalline varieties are, most often transparent and colorless, crystal habit refers to the shapes that crystals exhibit. Selenite crystals commonly occur as tabular, reticular, and columnar crystals, often with no imperfections or inclusions, many collectible selenite crystals have interesting inclusions such as, accompanying related minerals, interior druse, dendrites, and fossils. In some rare instances, water was encased as a fluid inclusion when the crystal formed, selenite crystals sometimes form in thin tabular or mica-like sheets and have been used as glass panes as at Santa Sabina in Rome. Selenite crystals sometimes will also exhibit bladed rosette habit often with accompanying transparent, selenite crystals can be found both attached to a matrix or base rock, but can commonly be found as entire free-floating crystals, often in clay beds. Satin spar is almost always prismatic and fibrous in a crystal habit. Satin spar often occurs in seams, some of them quite long, desert roses are most often bladed, exhibiting the familiar shape of a rose, and almost always have an exterior druse. Desert roses are almost always unattached to a matrix or base rock, gypsum flowers are most often acicular, scaly, stellate, and lenticular. Selenite crystals can also exhibit “arrow/spear-head” as well as “duck-bill” twins, both selenite crystals and gypsum flowers sometimes form quite densely in acicular mats or nets, and can be quite brittle and fragile. Gypsum flowers are attached to a matrix or base rock. Gypsum crystals are colorless, white, gray, brown, beige, orange, pink, yellow, light red, and green. Colors are caused by the presence of mineral inclusions such as, copper ores, sulfur and sulfides, silver, iron ores, coal, calcite, dolomite
Selenite (mineral)
–
Selenite
Selenite (mineral)
–
Selenite cluster from
Naica mine,
Chihuahua, Mexico
Selenite (mineral)
–
Selenite
Gypsum crystal
Selenite (mineral)
–
Desert rose
23.
Alabaster
–
Alabaster is a mineral or rock that is soft and often used for carving, as well as being processed for plaster powder. The term is used in different ways by archaeologists and the processing industry on the one hand. The first use is in a meaning, covering varieties of two different minerals, the fine-grained massive type of gypsum, as well as the fine-grained banded type of calcite. Geologists only define the gypsum variety as alabaster, chemically, gypsum is a hydrous sulfate of calcium, while calcite is a carbonate of calcium. Both types of alabaster have broadly similar properties and they are usually light-coloured, translucent and soft stones that have been used throughout human history mainly for carving decorative artifacts. Onyx-marble must be understood as a traditional, but geologically inaccurate term, in general, ancient alabaster is calcite in the wider Middle East, including Egypt and Mesopotamia, while it is gypsum in medieval Europe. Modern alabaster is calcite, but may be either. Both are easy to work and slightly water-soluble and they have been used for making a variety of indoor artworks and carvings, as they will not survive long outdoors. Moreover, calcite alabaster, being a carbonate, effervesces when treated with hydrochloric acid, the origin of the word alabaster is in Middle English through Old French alabastre, in turn derived from the Latin alabaster, and that from Greek ἀλάβαστρος or ἀλάβαστος. The Greek words were used to identify a vase made of alabaster and this name may be derived further from the Ancient Egyptian word a-labaste, which refers to vessels of the Egyptian goddess Bast. She was represented as a lioness and frequently depicted as such in figures placed atop these alabaster vessels, other suggestions include derivation from the town of Alabastron in Egypt, described in sometimes contradictory manner by Roman-era authors Pliny and Ptolemy and whose location is not yet known. The purest alabaster is a material of fine uniform grain, but it often is associated with an oxide of iron. The coarser varieties of gypsum alabaster are converted by calcination into plaster of Paris, the softness of alabaster enables it to be carved readily into elaborate forms, but its solubility in water renders it unsuitable for outdoor work. If alabaster with a smooth, polished surface is washed with dishwashing liquid, it will become rough, dull and whiter, losing most of its translucency and lustre. The finer kinds of alabaster are employed largely as a stone, especially for ecclesiastical decoration and for the rails of staircases. Alabaster is mined and then sold in blocks to alabaster workshops, the effect of heating appears to be a partial dehydration of the gypsum. If properly treated, it closely resembles true marble and is known as marmo di Castellina. Alabaster is a stone and can be dyed into any colour or shade
Alabaster
–
Three Maries, alabaster sculpture by Master of the Rimini Crucifixion (c. 1430),
National Museum,
Warsaw.
Alabaster
–
Alabaster
kohl pot from
Ancient Egypt
Alabaster
–
Statue made of alabaster,
Yemen
Alabaster
–
Alabaster tomb monument to Sir
Nicholas Fitzherbert
24.
Sulfate mineral
–
The sulfate minerals are a class of minerals which include the sulfate ion within their structure. The chromate and manganate minerals have a structure and are often included with the sulfates in mineral classification systems. This list uses it to modify the Classification of Nickel–Strunz
Sulfate mineral
–
Barite with
cerussite
Sulfate mineral
–
Anhydrite crystal structure
Sulfate mineral
–
Hanksite, one of the rare minerals that is a sulfate and carbonate
25.
Calcium sulfate
–
Calcium sulfate is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite, it is used as a desiccant, one particular hydrate is better known as plaster of Paris, and another occurs naturally as the mineral gypsum. It has many uses in industry, all forms are white solids that are poorly soluble in water. Calcium sulfate causes permanent hardness in water, the compound exists in three levels of hydration, anhydrous state with the formula CaSO4. Specific hemihydrates are sometimes distinguished, alpha-hemihydrate and beta-hemihydrate, the main use of calcium sulfate is to produce Plaster of Paris and stucco. These applications exploit the fact that calcium sulfate forms a moldable paste upon hydration and it is also convenient that calcium sulfate is very poorly soluble in water, so structures do not dissolve. Temperatures between 100 °C and 150 °C are required to drive off the water within its structure, the details of the temperature and time depend on ambient humidity. Temperatures as high as 170 °C are used in industrial calcination, in a fire, the structure behind a sheet of drywall will remain relatively cool as water is lost from the gypsum, thus preventing damage to the framing and consequent structural collapse. But at higher temperatures, calcium sulfate will release oxygen and act as an oxidizing agent and this property is used in aluminothermy. Mixed with polymers, it has used as a bone repair cement. Small amounts of calcined gypsum are added to earth to create strong structures directly from cast earth, the conditions of dehydration can be changed to adjust the porosity of the hemihydrate, resulting in the so-called alpha and beta hemihydrates. On heating to 180 °C, the nearly water-free form, called γ-anhydrite is produced, γ-Anhydrite reacts slowly with water to return to the dihydrate state, a property exploited in some commercial desiccants. On heating above 250 °C, the anhydrous form called β-anhydrite or natural anhydrite is formed. Natural anhydrite does not react with water, even over geological timescales, the hydrates are used as a coagulant in products such as tofu. Up to the 1970s, commercial quantities of sulfuric acid were produced from the anhydride of calcium sulfate, when sold as a color-indicating variant under the name Drierite, it appears blue or pink due to impregnation with cobalt chloride, which functions as a moisture indicator. The main sources of sulfate are naturally occurring gypsum and anhydrite. These may be extracted by open-cast quarrying or by deep mining, world production of natural gypsum is around 127 million tonnes per annum. This produces an impure calcium sulfite, which oxidizes on storage to calcium sulfate, in the production of phosphoric acid from phosphate rock, calcium phosphate is treated with sulfuric acid and calcium sulfate precipitates
Calcium sulfate
–
Calcium sulfate
26.
Hydrate
–
In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understood, in organic chemistry, a hydrate is a compound formed by the addition of water or its elements to another molecule. A molecule of water may be eliminated, for example by the action of sulfuric acid, another example is chloral hydrate, CCl3–CH2, which can be formed by reaction of water with chloral, CCl3–CH=O. Many organic molecules, as well as molecules, form crystals that incorporate water into the crystalline structure without chemical alteration of the organic molecule. The sugar trehalose, for example, exists in both a form and as a dihydrate. Protein crystals commonly have as much as 50% water content, molecules are also labeled as hydrates for historical reasons not covered above. Glucose, C6H12O6, was thought of as C66 and described as a carbohydrate. Methanol is often sold as methyl hydrate, implying the incorrect formula CH3OH2, such hydrates are also said to contain water of crystallization or water of hydration. If the water is water, where the hydrogen involved is the isotope deuterium. A colorful example is cobalt chloride, which turns blue to red upon hydration. The notation hydrated compound⋅nH2O, where n is the number of molecules per formula unit of the salt, is commonly used to show that a salt is hydrated. The n is usually a low integer, though it is possible for fractional values to occur, for example, in a monohydrate n is one, and in a hexahydrate n is 6. Numerical prefixes of Greek origin are, A hydrate which has lost water is referred to as an anhydride, a substance that does not contain any water is referred to as anhydrous. Some anhydrous compounds are hydrated so easily that they are said to be hygroscopic and are used as drying agents or desiccants, clathrate hydrates are water ice with gas molecules trapped within, they are a form of clathrate. An important example is methane hydrate, nonpolar molecules such as methane can form clathrate hydrates with water, especially under high pressure. In such cases the guest-host hydrogen bonds result in the formation of L-type Bjerrum defects in the clathrate lattice, the stability of hydrates is generally determined by the nature of the compounds, their temperature, and the relative humidity
Hydrate
–
Anhydrous cobalt(II) chloride CoCl 2
Hydrate
27.
Fertilizer
–
A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soils or to plant tissues to supply one or more plant nutrients essential to the growth of plants. Fertilizers enhance the growth of plants and this goal is met in two ways, the traditional one being additives that provide nutrients. The second mode by which some fertilizers act is to enhance the effectiveness of the soil by modifying its water retention and aeration and this article, like many on fertilizers, emphasises the nutritional aspect. The nutrients required for plant life are classified according to the elements. Instead compounds containing these elements are the basis of fertilizers, the macronutrients are consumed in larger quantities and are present in plant tissue in quantities from 0. 15% to 6. 0% on a dry matter basis. Plants are made up of four elements, hydrogen, oxygen, carbon. Carbon, hydrogen and oxygen are widely available as water and carbon dioxide, although nitrogen makes up most of the atmosphere, it is in a form that is unavailable to plants. Nitrogen is the most important fertilizer since nitrogen is present in proteins, DNA, to be nutritious to plants, nitrogen must be made available in a fixed form. Only some bacteria and their host plants can fix atmospheric nitrogen by converting it to ammonia, phosphate is required for the production of DNA and ATP, the main energy carrier in cells, as well as certain lipids. Micronutrients are consumed in quantities and are present in plant tissue on the order of parts-per-million, ranging from 0.15 to 400 ppm DM. These elements are present at the active sites of enzymes that carry out the plants metabolism. Because these elements enable catalysts their impact far exceeds their weight percentage, Fertilizers are classified in several ways. They are classified according to whether they provide a single nutrient, multinutrient fertilizers provide two or more nutrients, for example N and P. Fertilizers are also sometimes classified as inorganic versus organic. Inorganic fertilizers exclude carbon-containing materials except ureas, organic fertilizers are usually plant- or animal-derived matter. Inorganic are sometimes called synthetic fertilizers since various chemical treatments are required for their manufacture, the main nitrogen-based straight fertilizer is ammonia or its solutions. Ammonium nitrate is widely used. Urea is another source of nitrogen, having the advantage that it is solid and non-explosive, unlike ammonia and ammonium nitrate. A few percent of the fertilizer market has been met by calcium ammonium nitrate
Fertilizer
–
A large, modern fertilizer spreader
Fertilizer
–
A
Lite-Trac Agri-Spread
lime and fertilizer spreader at an agricultural show
Fertilizer
–
Compost bin for small-scale production of organic fertilizer
Fertilizer
–
A large commercial compost operation
28.
Plaster
–
Plaster is a building material used for the protective and/or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English plaster usually means a material used for the interiors of buildings, another imprecise term used for the material is stucco, which is also often used for plasterwork that is worked in some way to produce relief decoration, rather than flat surfaces. The most common types of plaster mainly contain either gypsum, lime, or cement, the plaster is manufactured as a dry powder and is mixed with water to form a stiff but workable paste immediately before it is applied to the surface. The reaction with water liberates heat through crystallization and the hydrated plaster then hardens, plaster can be relatively easily worked with metal tools or even sandpaper, and can be moulded, either on site or to make pre-formed sections in advance, which are put in place with adhesive. Plaster is not a material, it is suitable for finishing, rather than load-bearing. Forms of plaster have several other uses, in medicine plaster orthopedic casts are still often used for supporting set broken bones. In dentistry plaster is used to make dental models, various types of models and moulds are made with plaster. In art, lime plaster is the matrix for fresco painting. Gypsum plaster, or plaster of Paris, is produced by heating gypsum to about 300 °F, when the dry plaster powder is mixed with water, it re-forms into gypsum. The setting of unmodified plaster starts about 10 minutes after mixing and is complete in about 45 minutes, if plaster or gypsum is heated above 266 °F, hemihydrate is formed, which will also re-form as gypsum if mixed with water. On heating to 180 °C, the nearly water-free form, called γ-anhydrite is produced, γ-Anhydrite reacts slowly with water to return to the dihydrate state, a property exploited in some commercial desiccants. On heating above 250 °C, the anhydrous form called β-anhydrite or dead burned plaster is formed. A large gypsum deposit at Montmartre in Paris led calcined gypsum to be known as plaster of Paris. Plasterers often use gypsum to simulate the appearance of surfaces of wood, stone, or metal, on movie, nowadays, theatrical plasterers often use expanded polystyrene, although the job title remains unchanged. Plaster of Paris can be used to impregnate gauze bandages to make a material called plaster bandages. It is used similarly to clay, as it is shaped when wet, yet sets into a resilient. This is the material that was used to make classic plaster orthopedic casts to protect limbs with broken bones, set Modroc is an early example of a composite material. The hydration of plaster of Paris relies on the reaction of water with the dehydrated or partially hydrated calcium sulfate present in the plaster, lime plaster is a mixture of calcium hydroxide and sand
Plaster
–
Early 19th Century plasterer at work - painting by
John Cranch (1751 - 1821).
Plaster
–
19th century
stucco plasterwork from
House of Borujerdies in
Kashan,
Iran.
Plaster
–
19th century, plasterwork in
Mazandaran,
Behshahr,
Iran.
Plaster
–
Plasterwork in
Pompeii (79 AD)
29.
Blackboard
–
A blackboard is a reusable writing surface on which text or drawings are made with sticks of calcium sulfate or calcium carbonate, known, when used for this purpose, as chalk. Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone, a blackboard can simply be a piece of board painted with matte dark paint. Black plastic sign material, using the trade name sintra is also used to create custom chalkboard art, a more modern variation consists of a coiled sheet of plastic drawn across two parallel rollers, which can be scrolled to create additional writing space while saving what has been written. The highest grade blackboards are made of a rougher version porcelain enamelled steel, porcelain is very hard wearing and blackboards made of porcelain usually last 10–20 years in intensive use. Manufacturing of slate blackboards began by the 1840s, green chalkboards, generally made of porcelain enamel on a steel base, first appeared in the 1960s. Lecture theatres may contain a number of blackboards in a grid arrangement, the lecturer then moves boards into reach for writing and then moves them out of reach, allowing a large amount of material to be shown simultaneously. The chalk marks can be wiped off with a damp cloth. However, chalk marks made on some types of wet blackboard can be difficult to remove, sticks of processed chalk are produced especially for use with blackboards in white and also in various colours. These are often not from chalk rock but from calcium sulfate in its dihydrate form. Chalk sticks containing calcium carbonate typically contain 40-60% of CaCO3, as compared to whiteboards, blackboards have a variety of advantages, Chalk requires no special care, whiteboard markers must be capped or else they dry out. Chalk is an order of magnitude cheaper than whiteboard markers for a amount of writing. It is easier to draw lines of different weights and thicknesses with chalk than with whiteboard markers, dashed lines can be drawn very quickly using a technique involving the friction of the chalk and blackboard. Chalk has a smell, whereas whiteboard markers often have a pungent odor. Chalk writing often provides better contrast than whiteboard markers, Chalk can be easily erased, writing which has been left on a whiteboard for a prolonged period may require a solvent to remove. Chalk can be removed from most clothing, whiteboard markers often permanently stain fabric. On the other hand, chalk produces dust, the amount depending on the quality of chalk used, the dust also precludes the use of chalk in areas shared with dust-sensitive equipment such as computers. The writing on chalkboards is difficult to read in the dark, Chalk sticks are notorious for shrinking through use, and breaking in half unless inserted in a writing utensil designed to store chalk. According to a run by Michael Oehler, a professor at the University of Media and Communication in Cologne, Germany
Blackboard
–
A quadruple blackboard at the
Helsinki University of Technology
Blackboard
–
Students writing on a blackboard in a village school in
Laos
Blackboard
–
A modern green chalkboard that is designed to offer better readable contrasts.
Blackboard
–
Magnetic blackboard used for play and learning at the children's museum, Kitchener, Canada (The Museum)
30.
Drywall
–
Drywall is a panel made of calcium sulfate dihydrate with or without additives and normally pressed between a facer and a backer. It is used to make walls and ceilings. The plaster is mixed with fibre, plasticizer, foaming agent, and various additives that can decrease mildew, increase fire resistance, drywall construction became prevalent in North America as a speedier alternative to traditional lath and plaster. The first plasterboard plant in the UK was opened in 1888 in Rochester, Sackett Board was invented in 1894 by Augustine Sackett and Fred Kane. It was made by layering plaster within four plies of wool felt paper, sheets were 36 ×36 × 1/4 thick with open edges. Gypsum board evolved between 1910 and 1930 beginning with wrapped board edges and elimination of the two layers of felt paper in favor of paper-based facings. In 1910 United States Gypsum Corporation bought Sackett Plaster Board Company, providing efficiency of installation, it was developed additionally as a measure of fire resistance. Later air entrainment technology made boards lighter and less brittle, then joint treatment materials, rock lath was an early substrate for plaster. As it evolved, it was faced with paper impregnated with gypsum crystals that bonded with the applied facing layer of plaster, a wallboard panel consists of a layer of gypsum plaster sandwiched between two layers of paper. The raw gypsum, CaSO4·2 H2O, is heated to drive off the water then slightly rehydrated to produce the hemihydrate of calcium sulfate, the board is then formed by sandwiching a core of the wet mixture between two sheets of heavy paper or fibreglass mats. When the core sets it is dried in a large drying chamber. Drying chambers typically use natural gas today, to dry 1 MSF of wallboard, between 1,750,000 and 2,490,000 BTU is required. Organic dispersants/plasticisers are used so the slurry will flow during manufacture, coal-fired power stations include devices called scrubbers to remove sulphur from their exhaust emissions. The sulphur is absorbed by powdered limestone in a process called flue-gas desulphurization and this is commonly used in drywall construction in the United States and elsewhere. Drywall panels in the United States are manufactured in 48-inch, 54-inch and 96-inch wide panels in varying lengths to suit the application, lengths up to 12-feet are commonly available, though the most common length is 8-feet. Common panel thicknesses are 1⁄2-inch and 5⁄8-inch, with panels also available in 1⁄4-inch, 3⁄8-inch, 3/4-inch and 1-inch for specific applications, in Europe plasterboard is manufactured in metric sizes, with the common sizes being corollaries of old imperial sizes. Most plasterboard is made in 120 cm-wide sheets, though 90 cm and 60 cm wide sheets are also made,120 cm wide plasterboard is most commonly made in 240 cm lengths, though 250,260,270,280,300 cm and even longer are commonly available. Thicknesses of plasterboard available are 9.5 mm to 25 mm, however four side chamfered drywall is not currently offered by major UK manufacturers for general use
Drywall
–
Vertically hung drywall with
joint compound.
Drywall
–
Drywall is delivered to a building site on a flatbed truck and unloaded with a forked material handler crane. The bulk drywall sheets are unloaded directly to upper floors via a window or exterior doorway.
Drywall
–
Electric screw gun used to drive drywall screws
Drywall
–
Drywall water damage in a closet.
31.
Sculpture
–
Sculpture is the branch of the visual arts that operates in three dimensions. It is one of the plastic arts, a wide variety of materials may be worked by removal such as carving, assembled by welding or modelling, or molded, or cast. However, most ancient sculpture was painted, and this has been lost. Those cultures whose sculptures have survived in quantities include the cultures of the ancient Mediterranean, India and China, the Western tradition of sculpture began in ancient Greece, and Greece is widely seen as producing great masterpieces in the classical period. During the Middle Ages, Gothic sculpture represented the agonies and passions of the Christian faith, the revival of classical models in the Renaissance produced famous sculptures such as Michelangelos David. Relief is often classified by the degree of projection from the wall into low or bas-relief, high relief, sunk-relief is a technique restricted to ancient Egypt. Relief sculpture may also decorate steles, upright slabs, usually of stone, techniques such as casting, stamping and moulding use an intermediate matrix containing the design to produce the work, many of these allow the production of several copies. The term sculpture is used mainly to describe large works. The very large or colossal statue has had an enduring appeal since antiquity, another grand form of portrait sculpture is the equestrian statue of a rider on horse, which has become rare in recent decades. The smallest forms of life-size portrait sculpture are the head, showing just that, or the bust, small forms of sculpture include the figurine, normally a statue that is no more than 18 inches tall, and for reliefs the plaquette, medal or coin. Sculpture is an important form of public art, a collection of sculpture in a garden setting can be called a sculpture garden. One of the most common purposes of sculpture is in form of association with religion. Cult images are common in cultures, though they are often not the colossal statues of deities which characterized ancient Greek art. The actual cult images in the innermost sanctuaries of Egyptian temples, of which none have survived, were rather small. The same is true in Hinduism, where the very simple. Some undoubtedly advanced cultures, such as the Indus Valley civilization, appear to have had no monumental sculpture at all, though producing very sophisticated figurines, the Mississippian culture seems to have been progressing towards its use, with small stone figures, when it collapsed. Other cultures, such as ancient Egypt and the Easter Island culture, from the 20th century the relatively restricted range of subjects found in large sculpture expanded greatly, with abstract subjects and the use or representation of any type of subject now common. Today much sculpture is made for intermittent display in galleries and museums, small sculpted fittings for furniture and other objects go well back into antiquity, as in the Nimrud ivories, Begram ivories and finds from the tomb of Tutankhamun
Sculpture
–
The Dying Gaul, or The Capitoline Gaul a Roman marble copy of a
Hellenistic work of the late 3rd century BCE
Capitoline Museums, Rome
Sculpture
Sculpture
–
Michelangelo 's
Moses, (c. 1513–1515), housed in the church of
San Pietro in Vincoli in
Rome. The sculpture was commissioned in 1505 by
Pope Julius II for his
tomb.
Sculpture
–
Assyrian
lamassu gate guardian from
Khorsabad, c. 721–800 BCE
32.
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.
33.
Mesopotamia
–
In the Iron Age, it was controlled by the Neo-Assyrian and Neo-Babylonian Empires. The Sumerians and Akkadians dominated Mesopotamia from the beginning of history to the fall of Babylon in 539 BC. It fell to Alexander the Great in 332 BC, and after his death, around 150 BC, Mesopotamia was under the control of the Parthian Empire. Mesopotamia became a battleground between the Romans and Parthians, with parts of Mesopotamia coming under ephemeral Roman control. In AD226, eastern part of it fell to the Sassanid Persians, division of Mesopotamia between Roman and Sassanid Empires lasted until the 7th century Muslim conquest of Persia of the Sasanian Empire and Muslim conquest of the Levant from Byzantines. A number of primarily neo-Assyrian and Christian native Mesopotamian states existed between the 1st century BC and 3rd century AD, including Adiabene, Osroene, and Hatra, Mesopotamia is the site of the earliest developments of the Neolithic Revolution from around 10,000 BC. The regional toponym Mesopotamia comes from the ancient Greek root words μέσος middle and ποταμός river and it is used throughout the Greek Septuagint to translate the Hebrew equivalent Naharaim. In the Anabasis, Mesopotamia was used to designate the land east of the Euphrates in north Syria, the Aramaic term biritum/birit narim corresponded to a similar geographical concept. The neighbouring steppes to the west of the Euphrates and the part of the Zagros Mountains are also often included under the wider term Mesopotamia. A further distinction is made between Northern or Upper Mesopotamia and Southern or Lower Mesopotamia. Upper Mesopotamia, also known as the Jazira, is the area between the Euphrates and the Tigris from their sources down to Baghdad, Lower Mesopotamia is the area from Baghdad to the Persian Gulf and includes Kuwait and parts of western Iran. In modern academic usage, the term Mesopotamia often also has a chronological connotation and it is usually used to designate the area until the Muslim conquests, with names like Syria, Jazirah, and Iraq being used to describe the region after that date. It has been argued that these later euphemisms are Eurocentric terms attributed to the region in the midst of various 19th-century Western encroachments, Mesopotamia encompasses the land between the Euphrates and Tigris rivers, both of which have their headwaters in the Armenian Highlands. Both rivers are fed by tributaries, and the entire river system drains a vast mountainous region. Overland routes in Mesopotamia usually follow the Euphrates because the banks of the Tigris are frequently steep and difficult. The climate of the region is semi-arid with a vast desert expanse in the north which gives way to a 15,000 square kilometres region of marshes, lagoons, mud flats, in the extreme south, the Euphrates and the Tigris unite and empty into the Persian Gulf. In the marshlands to the south of the area, a complex water-borne fishing culture has existed since prehistoric times, periodic breakdowns in the cultural system have occurred for a number of reasons. Alternatively, military vulnerability to invasion from marginal hill tribes or nomadic pastoralists has led to periods of trade collapse and these trends have continued to the present day in Iraq
Mesopotamia
–
Known world of the Mesopotamian, Babylonian, and Assyrian cultures from documentary sources
Mesopotamia
–
Map showing the extent of Mesopotamia
Mesopotamia
–
One of 18
Statues of Gudea, a ruler around 2090 BC
Mesopotamia
–
One of the
Nimrud ivories shows a lion eating a man. Neo-Assyrian period, 9th to 7th centuries BC.
34.
Ancient Rome
–
In its many centuries of existence, the Roman state evolved from a monarchy to a classical republic and then to an increasingly autocratic empire. Through conquest and assimilation, it came to dominate the Mediterranean region and then Western Europe, Asia Minor, North Africa and it is often grouped into classical antiquity together with ancient Greece, and their similar cultures and societies are known as the Greco-Roman world. Ancient Roman civilisation has contributed to modern government, law, politics, engineering, art, literature, architecture, technology, warfare, religion, language and society. Rome professionalised and expanded its military and created a system of government called res publica, the inspiration for modern republics such as the United States and France. By the end of the Republic, Rome had conquered the lands around the Mediterranean and beyond, its domain extended from the Atlantic to Arabia, the Roman Empire emerged with the end of the Republic and the dictatorship of Augustus Caesar. 721 years of Roman-Persian Wars started in 92 BC with their first war against Parthia and it would become the longest conflict in human history, and have major lasting effects and consequences for both empires. Under Trajan, the Empire reached its territorial peak, Republican mores and traditions started to decline during the imperial period, with civil wars becoming a prelude common to the rise of a new emperor. Splinter states, such as the Palmyrene Empire, would divide the Empire during the crisis of the 3rd century. Plagued by internal instability and attacked by various migrating peoples, the part of the empire broke up into independent kingdoms in the 5th century. This splintering is a landmark historians use to divide the ancient period of history from the pre-medieval Dark Ages of Europe. King Numitor was deposed from his throne by his brother, Amulius, while Numitors daughter, Rhea Silvia, because Rhea Silvia was raped and impregnated by Mars, the Roman god of war, the twins were considered half-divine. The new king, Amulius, feared Romulus and Remus would take back the throne, a she-wolf saved and raised them, and when they were old enough, they returned the throne of Alba Longa to Numitor. Romulus became the source of the citys name, in order to attract people to the city, Rome became a sanctuary for the indigent, exiled, and unwanted. This caused a problem for Rome, which had a large workforce but was bereft of women, Romulus traveled to the neighboring towns and tribes and attempted to secure marriage rights, but as Rome was so full of undesirables they all refused. Legend says that the Latins invited the Sabines to a festival and stole their unmarried maidens, leading to the integration of the Latins, after a long time in rough seas, they landed at the banks of the Tiber River. Not long after they landed, the men wanted to take to the sea again, one woman, named Roma, suggested that the women burn the ships out at sea to prevent them from leaving. At first, the men were angry with Roma, but they realized that they were in the ideal place to settle. They named the settlement after the woman who torched their ships, the Roman poet Virgil recounted this legend in his classical epic poem the Aeneid
Ancient Rome
–
Senātus Populus que Rōmānus
Ancient Rome
–
Roman Republic
Ancient Rome
–
According to legend,
Rome was founded in 753 BC by
Romulus and Remus, who were raised by a she-wolf.
Ancient Rome
–
This bust from the
Capitoline Museums is traditionally identified as a portrait of
Lucius Junius Brutus.
35.
Byzantine Empire
–
It survived the fragmentation and fall of the Western Roman Empire in the 5th century AD and continued to exist for an additional thousand years until it fell to the Ottoman Turks in 1453. During most of its existence, the empire was the most powerful economic, cultural, several signal events from the 4th to 6th centuries mark the period of transition during which the Roman Empires Greek East and Latin West divided. Constantine I reorganised the empire, made Constantinople the new capital, under Theodosius I, Christianity became the Empires official state religion and other religious practices were proscribed. Finally, under the reign of Heraclius, the Empires military, the borders of the Empire evolved significantly over its existence, as it went through several cycles of decline and recovery. During the reign of Maurice, the Empires eastern frontier was expanded, in a matter of years the Empire lost its richest provinces, Egypt and Syria, to the Arabs. This battle opened the way for the Turks to settle in Anatolia, the Empire recovered again during the Komnenian restoration, such that by the 12th century Constantinople was the largest and wealthiest European city. Despite the eventual recovery of Constantinople in 1261, the Byzantine Empire remained only one of several small states in the area for the final two centuries of its existence. Its remaining territories were annexed by the Ottomans over the 15th century. The Fall of Constantinople to the Ottoman Empire in 1453 finally ended the Byzantine Empire, the term comes from Byzantium, the name of the city of Constantinople before it became Constantines capital. This older name of the city would rarely be used from this point onward except in historical or poetic contexts. The publication in 1648 of the Byzantine du Louvre, and in 1680 of Du Canges Historia Byzantina further popularised the use of Byzantine among French authors, however, it was not until the mid-19th century that the term came into general use in the Western world. The Byzantine Empire was known to its inhabitants as the Roman Empire, the Empire of the Romans, Romania, the Roman Republic, Graikia, and also as Rhōmais. The inhabitants called themselves Romaioi and Graikoi, and even as late as the 19th century Greeks typically referred to modern Greek as Romaika and Graikika. The authority of the Byzantine emperor as the legitimate Roman emperor was challenged by the coronation of Charlemagne as Imperator Augustus by Pope Leo III in the year 800. No such distinction existed in the Islamic and Slavic worlds, where the Empire was more seen as the continuation of the Roman Empire. In the Islamic world, the Roman Empire was known primarily as Rûm, the Roman army succeeded in conquering many territories covering the entire Mediterranean region and coastal regions in southwestern Europe and north Africa. These territories were home to different cultural groups, both urban populations and rural populations. The West also suffered heavily from the instability of the 3rd century AD
Byzantine Empire
–
Tremissis with the image of
Justinian the Great (r. 527–565) (see
Byzantine insignia)
Byzantine Empire
–
Byzantine
lamellar armour klivanium (Κλιβάνιον) - a predecessor of Ottoman krug
mirror armour
Byzantine Empire
–
The Baptism of Constantine painted by
Raphael 's pupils (1520–1524,
fresco, Vatican City,
Apostolic Palace);
Eusebius of Caesarea records that (as
was common among converts of early Christianity) Constantine delayed receiving
baptism until shortly before his death
Byzantine Empire
–
Restored section of the Theodosian Walls.
36.
Nottingham alabaster
–
Alabaster carvers were at work in London, York and Burton-on-Trent, and many probably worked very close to the rural mines, but the largest concentration was around Nottingham. This has led to all the English medieval output being referred to as Nottingham alabaster, Alabaster is a mineral composed of gypsum and various impurities, is much softer and easier to work than marble and a good material for mass production, though not suitable for outdoors use. These were attractive for less wealthy churches, and for the chapels of the nobility. Some complete ensembles survive, showing varied numbers of panels, the dimensions of the Nativity illustrated are typical. The subjects were the same as in painted altarpieces, often including short cycles of the Life of Christ, especially the Passion of Christ, since the sets were probably generally not made to a specific commission, unlike paintings, there are fewer local or patron saints. Throughout the period of their production Nottingham alabaster images were popular in Europe and were exported in large quantities, some ending up as far afield as Iceland, Croatia. The alabaster used in the industry was quarried largely in the area around South Derbyshire near Tutbury, the craftsmen were known by various names such as alabastermen, kervers, marblers, and image-makers. The tomb of John of Eltham, Earl of Cornwall, who died in 1334, in Westminster Abbey, is an early example, the execution of this order cost £200 and required 10 carts,80 horses, and 20 men to transport it to its destination. The journey occupied seventeen days in the autumn of 1367, the church at Tong, Shropshire contains an especially fine sequence of tombs of the Vernon family spanning the 15th and 16th centuries. Indeed, eight months after this act, in January 1550 the English Ambassador to France reported the arrival of three English ships laden with alabaster images to be sold at Paris, Rouen and elsewhere. Whether these were new images, or ones removed from English churches, is not entirely clear, from the middle of the sixteenth century, workshops focused instead on sculpting alabaster tombs or church monuments, which were not affected by Protestant aniconism. Indeed, these were becoming larger and more elaborate, and were now taken up by the merchant classes as well as the nobility. Vertical monuments placed against walls generally replaced the older recumbent effigies, there is an elaborate relief panel of Apollo and the Muses, of about 1580, which is probably English, in the Victoria and Albert Museum. The sculpture industry evolved to two main forms, panels and statues. Many statues were smaller than this, but there are a number of larger ones, an example of a much larger statue, three feet high and free-standing but flat-backed, is Our Lady of Westminster, now in London but found by the art trade in France. Exports, as of the better documented contemporary export trade in icons of the Cretan school, were made in bulk for sale to dealers. Most surviving examples have lost much of their paintwork, but the colouring of the carvings was a part of the production. Moulded and gilded gesso was also used to give extra richness to the carvings which would need to be brightly coloured, the subjects of the sculptors were the usual content of altarpieces, most often scenes from the Life of Christ or Life of the Virgin
Nottingham alabaster
–
Resurrection of Christ, panel from an altarpiece set, 1450–90, with remains of the paint
Nottingham alabaster
–
Nativity panel, ca 1400, using a composition previously found in French ivories. H. 37.5 cm (14 ¾ in.), W. 26 cm (10 in.), D. 4.5 cm (1 ¾ in.)
Nottingham alabaster
–
detail of the tomb of Sir
Ralph Fitzherbert, d. 1483, showing some of his children.
Nottingham alabaster
–
Monument to Edmund Brudenell, d.1590. After the
English Reformation tomb monuments were the mainstay of the industry.
37.
Medieval England
–
England in the Middle Ages concerns the history of England during the medieval period, from the end of the 5th century through to the start of the Early Modern period in 1485. When England emerged from the collapse of the Roman Empire, the economy was in tatters, after several centuries of Germanic immigration, new identities and cultures began to emerge, developing into predatory kingdoms that competed for power. A rich artistic culture flourished under the Anglo-Saxons, producing epic poems such as Beowulf, the Anglo-Saxons converted to Christianity in the 7th century and a network of monasteries and convents were built across England. The Norman invasion of England in 1066 led to the defeat and replacement of the Anglo-Saxon elite with Norman and French nobles, William the Conqueror and his successors took over the existing state system, repressing local revolts and controlling the population through a network of castles. The new rulers introduced an approach to governing England, eradicating the practice of slavery. The position of women in society changed as laws regarding land, Englands population more than doubled during the 12th and 13th centuries, fuelling an expansion of the towns, cities and trade, helped by warmer temperatures across Northern Europe. A new wave of monasteries and friaries were established, while ecclesiastical reforms led to tensions between successive kings and archbishops, despite developments in Englands governance and legal system, infighting between the Anglo-Norman elite resulted in multiple civil wars and the loss of Normandy. Nearly 1,500 villages were deserted by their inhabitants and many men and women sought new opportunities in the towns, new technologies were introduced, and England produced some of the great medieval philosophers and natural scientists. English kings in the 14th and 15th centuries laid claim to the French throne, more social unrest broke out, followed by the Wars of the Roses, fought between rival factions in the English nobility. Henry VIIs victory in 1485 typically marks the end of the Middle Ages in England, at the start of the Middle Ages, England was a part of Britannia, a former province of the Roman Empire. The English economy had once dominated by imperial Roman spending on a large military establishment, which in turn helped to support a complex network of towns, roads. At the end of the 4th century, however, Roman forces had largely withdrawn. Germanic immigrants began to arrive in increasing numbers during the 5th century, initially peacefully, establishing small farms, in the 7th century, the kingdom of Mercia rose to prominence under the leadership of King Penda. Mercia invaded neighbouring lands until it loosely controlled around 50 regiones covering much of England, Mercia and the remaining kingdoms, led by their warrior elites, continued to compete for territory throughout the 8th century. Massive earthworks, such as the dyke built by Offa of Mercia, helped to defend key frontiers. Mercia and Northumbria fell in 875 and 876, and Alfred of Wessex was driven into exile in 878. Suppressing internal opposition to his rule, Alfred contained the invaders within a known as the Danelaw. The West Saxon rulers were now kings of the Angelcynn, that is of the whole English folk, with the death of Edgar, however, the royal succession became problematic
Medieval England
–
Clockwise, from top left: Detail of the 11th-century
Bayeux Tapestry, showing
Harold Godwinson; 15th-century stained glass from
York Minster, showing a scene from
the Apocalypse;
Salisbury Cathedral, built in the 13th century; the 9th-century
Ormside Bowl
Medieval England
–
Ceremonial
Anglo-Saxon helmet from the
Sutton Hoo burial, 7th century
Medieval England
–
Section of the Bayeux Tapestry showing the final stages of the
battle of Hastings
Medieval England
–
Richard II meets the rebels calling for economic and political reform during the
Peasants' Revolt of 1381
38.
Evaporite
–
Evaporite is a name for a water-soluble mineral sediment that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of deposits, marine, which can also be described as ocean deposits, and non-marine. Evaporites are considered sedimentary rocks and are formed by chemical sediments, although all water bodies on the surface and in aquifers contain dissolved salts, the water must evaporate into the atmosphere for the minerals to precipitate. For this to happen, the body must enter a restricted environment where water input into this environment remains below the net rate of evaporation. This is usually an arid environment with a basin fed by a limited input of water. When evaporation occurs, the water is enriched in salts. Marine evaporites tend to have thicker deposits and are usually the focus of extensive research. They also have a system of evaporation, when scientists evaporate ocean water in a laboratory, the minerals are deposited in a defined order that was first demonstrated by Usiglio in 1884. The first phase of the experiment begins when about 50% of the water depth remains. At this point, minor carbonates begin to form, the next phase in the sequence comes when the experiment is left with about 20% of its original level. At this point, the mineral gypsum begins to form, which is followed by halite at 10%. Kieserite may also be included, which often make up less than four percent of the overall content. However, there are approximately 80 different minerals that have been reported found in evaporite deposits, common minerals that are found in these deposits include blödite, borax, epsomite, gaylussite, glauberite, mirabilite, thenardite and trona. Non-marine deposits may also contain halite, gypsum, and anhydrite and this, however, does not make non-marine deposits any less important, these deposits often help to paint a picture into past Earth climates. Some particular deposits even show important tectonic and climatic changes and these deposits also may contain important minerals that help in todays economy. Thick non-marine deposits that tend to form where evaporation rates will exceed the inflow rate. The inflow also has to occur in a basin, or one with restricted outflow, so that the sediment has time to pool. Primary examples of this are called saline lake deposits, examples of modern non-marine depositional environments include the Great Salt Lake in Utah and the Dead Sea, which lies between Jordan and Israel
Evaporite
–
Cobble encrusted with
halite evaporated from the
Dead Sea, Israel.
Evaporite
–
Anhydrite
Evaporite
–
Hopper crystal cast of
halite in a
Jurassic rock, Carmel Formation, southwestern Utah.
Evaporite
–
Calcite
39.
Anhydrite
–
Anhydrite is a mineral—anhydrous calcium sulfate, CaSO4. It is in the crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the orthorhombic barium and strontium sulfates, distinctly developed crystals are somewhat rare, the mineral usually presenting the form of cleavage masses. The Mohs hardness is 3.5 and the gravity is 2.9. The color is white, sometimes greyish, bluish, or purple, on the best developed of the three cleavages, the lustre is pearly, on other surfaces it is glassy. When exposed to water, anhydrite readily transforms to the commonly occurring gypsum. This transformation is reversible, with gypsum or calcium sulfate hemihydrate forming anhydrite by heating to around 200 °C under normal atmospheric conditions, anhydrite is commonly associated with calcite, halite, and sulfides such as galena, chalcopyrite, molybdenite, and pyrite in vein deposits. Anhydrite is most frequently found in deposits with gypsum, it was, for instance, first discovered, in 1794. In this occurrence, depth is critical since nearer the surface anhydrite has been altered to gypsum by absorption of circulating ground water and this is one of the several methods by which the mineral has been prepared artificially, and is identical with its mode of origin in nature. The mineral is common in salt basins, anhydrite occurs in a tidal flat environment in the Persian Gulf sabkhas as massive diagenetic replacement nodules. Cross sections of these nodular masses have an appearance and have been referred to as chicken-wire anhydrite. Nodular anhydrite occurs as replacement of gypsum in a variety of depositional environments. Massive amounts of anhydrite occur when salt domes form a caprock, anhydrite is 1–3% of the salt in salt domes and is generally left as a cap at the top of the salt when the halite is removed by pore waters. The typical cap rock is a salt, topped by a layer of anhydrite, topped by patches of gypsum, interaction with oil can reduce SO4 creating calcite, water, and hydrogen sulfide. Anhydrite has been found in igneous rocks, for example in the intrusive dioritic pluton of El Teniente, Chile and in trachyandesite pumice erupted by El Chichón volcano. The name anhydrite was given by A. G. Werner in 1804, because of the absence of water of crystallization, as contrasted with the presence of water in gypsum. Some obsolete names for the species are muriacite and karstenite, the former, the Catalyst Science Discovery Centre, Widnes, has a relief carving of an anhydrite kiln, made from a piece of anhydrite, for the United Sulphuric Acid Corporation
Anhydrite
–
Anhydrite, Chihuahua, Mexico
Anhydrite
–
Relief carving of an anhydrite kiln, made from a piece of anhydrite, by
Ophelia Gordon Bell
40.
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
41.
Quarry
–
A quarry is a place from which dimension stone, rock, construction aggregate, riprap, sand, gravel, or slate has been excavated from the ground. A quarry is the thing as an open-pit mine from which minerals are extracted. The only non-trivial difference between the two is that open-pit mines that produce building materials and dimension stone are commonly referred to as quarries, the word quarry can also include the underground quarrying for stone, such as Bath stone. The surfaces are polished and finished with varying degrees of sheen or luster, polished slabs are often cut into tiles or countertops and installed in many kinds of residential and commercial properties. Natural stone quarried from the earth is considered a luxury and tends to be a highly durable surface. Quarries in level areas with shallow groundwater or which are located close to surface water often have engineering problems with drainage, generally the water is removed by pumping while the quarry is operational, but for high inflows more complex approaches may be required. For example, the Coquina quarry is excavated to more than 60 feet below sea level, to reduce surface leakage, a moat lined with clay was constructed around the entire quarry. Ground water entering the pit is pumped up into the moat, as a quarry becomes deeper, water inflows generally increase and it also becomes more expensive to lift the water higher during removal, this can become the limiting factor in quarry depth. Some water-filled quarries are worked from beneath the water, by dredging, many people and municipalities consider quarries to be eyesores and require various abatement methods to address problems with noise, dust, and appearance. One of the effective and famous examples of successful quarry restoration is Butchart Gardens in Victoria, BC. A further problem is pollution of roads from trucks leaving the quarries, to control and restrain the pollution of public roads, wheel washing systems are becoming more common. Many quarries naturally fill with water after abandonment and become lakes, water-filled quarries can be very deep with water, often 50 feet or more, that is often surprisingly cold. Unexpectedly cold water can cause a swimmers muscles to weaken, it can also cause shock. Though quarry water is very clear, submerged quarry stones. Several people drown in quarries each year, however, many inactive quarries are converted into safe swimming sites
Quarry
–
Carrara quarry in
Tuscany,
Italy.
Quarry
–
Portland stone quarry on the
Isle of Portland, England
Quarry
–
An abandoned
construction aggregate quarry near
Adelaide,
South Australia
Quarry
–
Stone quarry in
Soignies,
Hainaut (province), Belgium.
42.
Montmartre
–
Montmartre is a large hill in Pariss 18th arrondissement. It is 130 m high and gives its name to the surrounding district, Montmartre is primarily known for the white-domed Basilica of the Sacré-Cœur on its summit and as a nightclub district. The other, older, church on the hill is Saint Pierre de Montmartre, Montmartre is also the setting for several hit films. This site is served by metro, with line 2 stations at Anvers, Pigalle, and Blanche and line 12 stations at Pigalle, Abbesses, Lamarck - Caulaincourt, texts from the 8th century cite the name of mons Mercori, and a 9th-century text speaks of Mount Mars. Excavations in 1975 north of the Church of Saint-Pierre found coins from the 3rd century, earlier excavations in the 17th century at the Fontaine-du-But found vestiges of Roman baths from the 2nd century. According to Hilduin, Denis collected his head and carried it as far as the fontaine Saint-Denis, then descended the slope of the hill. Hilduin wrote that a church had built in the place formerly called Mont de Mars. In 1134, king Louis VI purchased the Merovingian chapel and built on the site the church of Saint-Pierre de Montmartre and he also founded The Royal Abbey of Montmartre, a monastery of the Benedictine order, whose buildings, gardens and fields occupied most of Montmartre. He also built a chapel, called the Martyrium, at the site where it was believed that Saint Denis had been decapitated. It became a pilgrimage site. In the 17th century, a priory called abbaye den bas was built at that site, the abbey was destroyed in 1790 during the French Revolution, and the convent demolished to make place for gypsum mines. The church of Saint-Pierre was saved, at the place where the chapel of the Martyrs was located, an oratory was built in 1855. By the 15th century, the north and northeast slopes of the hill were the site of a surrounded by vineyards, gardens and orchards of peach. The first mills were built on the slope in 1529, grinding wheat, barley. The siege eventually failed when a relief force approached and forced Henry to withdraw. In 1790, Montmartre was located just outside the limits of Paris and that year, under the revolutionary government of the National Constituent Assembly, it became the commune of Montmartre, with its town hall located on place du Tertre, site of the former abbey. The main businesses of the commune were wine making, stone quarries, the mining of gypsum had begun in the Gallo-Roman period, first in open air mines and then underground, and continued until 1860. The gypsum was cut into blocks, baked, then ground, sold as montmartarite, it was used for plaster, because of its resistance to fire and water
Montmartre
–
Montmartre, dominated by the
Basilica of the Sacré Cœur
Montmartre
–
Saint-Pierre de Montmartre (1133) seen from the dome of the Basilica of the Sacré-Cœur.
Montmartre
–
The Moulin de la Galette, painted by
Vincent Van Gogh in 1887 (Carnegie Museum of Art).
Montmartre
–
The Chapel of the Martyrs of Monmartre Abbey in the 17th century
43.
Paris
–
Paris is the capital and most populous city of France. It has an area of 105 square kilometres and a population of 2,229,621 in 2013 within its administrative limits, the agglomeration has grown well beyond the citys administrative limits. By the 17th century, Paris was one of Europes major centres of finance, commerce, fashion, science, and the arts, and it retains that position still today. The aire urbaine de Paris, a measure of area, spans most of the Île-de-France region and has a population of 12,405,426. It is therefore the second largest metropolitan area in the European Union after London, the Metropole of Grand Paris was created in 2016, combining the commune and its nearest suburbs into a single area for economic and environmental co-operation. Grand Paris covers 814 square kilometres and has a population of 7 million persons, the Paris Region had a GDP of €624 billion in 2012, accounting for 30.0 percent of the GDP of France and ranking it as one of the wealthiest regions in Europe. The city is also a rail, highway, and air-transport hub served by two international airports, Paris-Charles de Gaulle and Paris-Orly. Opened in 1900, the subway system, the Paris Métro. It is the second busiest metro system in Europe after Moscow Metro, notably, Paris Gare du Nord is the busiest railway station in the world outside of Japan, with 262 millions passengers in 2015. In 2015, Paris received 22.2 million visitors, making it one of the top tourist destinations. The association football club Paris Saint-Germain and the rugby union club Stade Français are based in Paris, the 80, 000-seat Stade de France, built for the 1998 FIFA World Cup, is located just north of Paris in the neighbouring commune of Saint-Denis. Paris hosts the annual French Open Grand Slam tennis tournament on the red clay of Roland Garros, Paris hosted the 1900 and 1924 Summer Olympics and is bidding to host the 2024 Summer Olympics. The name Paris is derived from its inhabitants, the Celtic Parisii tribe. Thus, though written the same, the name is not related to the Paris of Greek mythology. In the 1860s, the boulevards and streets of Paris were illuminated by 56,000 gas lamps, since the late 19th century, Paris has also been known as Panam in French slang. Inhabitants are known in English as Parisians and in French as Parisiens and they are also pejoratively called Parigots. The Parisii, a sub-tribe of the Celtic Senones, inhabited the Paris area from around the middle of the 3rd century BC. One of the areas major north-south trade routes crossed the Seine on the île de la Cité, this place of land and water trade routes gradually became a town
Paris
–
In the 1860s Paris streets and monuments were illuminated by 56,000 gas lamps, making it literally "The City of Light."
Paris
Paris
–
Gold coins minted by the Parisii (1st century BC)
Paris
–
The
Palais de la Cité and
Sainte-Chapelle, viewed from the Left Bank, from the
Très Riches Heures du duc de Berry (month of June) (1410)
44.
Calcination
–
Authorities differ on the meaning of calcination. The IUPAC defines it as heating to temperatures in air or oxygen. A calciner is a cylinder that rotates inside a heated furnace. The product of calcination is usually referred to in general as calcine, calcination is carried out in furnaces or reactors of various designs including shaft furnaces, rotary kilns, multiple hearth furnaces, and fluidized bed reactors. Calcination reactions usually take place at or above the decomposition temperature or the transition temperature. This temperature is defined as the temperature at which the standard Gibbs free energy for a particular calcination reaction is equal to zero. For example, in limestone calcination, a process, the chemical reaction is CaCO3 → CaO + CO2 The standard Gibbs free energy of reaction is approximated as ΔG°r =177,100 −158 T. The standard free energy of reaction is 0 in this case when the temperature, T, is equal to 1121 K, see also calcination equilibrium of calcium carbonate In some cases, calcination of a metal results in oxidation of the metal. Jean Rey noted that lead and tin when calcinated gained weight, in alchemy, calcination was believed to be one of the 12 vital processes required for the transformation of a substance. Alchemists distinguished two kinds of calcination, actual and potential, actual calcination is that brought about by actual fire, from wood, coals, or other fuel, raised to a certain temperature
Calcination
–
An oven for calcination of limestone
45.
Plaster of Paris
–
Plaster is a building material used for the protective and/or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English plaster usually means a material used for the interiors of buildings, another imprecise term used for the material is stucco, which is also often used for plasterwork that is worked in some way to produce relief decoration, rather than flat surfaces. The most common types of plaster mainly contain either gypsum, lime, or cement, the plaster is manufactured as a dry powder and is mixed with water to form a stiff but workable paste immediately before it is applied to the surface. The reaction with water liberates heat through crystallization and the hydrated plaster then hardens, plaster can be relatively easily worked with metal tools or even sandpaper, and can be moulded, either on site or to make pre-formed sections in advance, which are put in place with adhesive. Plaster is not a material, it is suitable for finishing, rather than load-bearing. Forms of plaster have several other uses, in medicine plaster orthopedic casts are still often used for supporting set broken bones. In dentistry plaster is used to make dental models, various types of models and moulds are made with plaster. In art, lime plaster is the matrix for fresco painting. Gypsum plaster, or plaster of Paris, is produced by heating gypsum to about 300 °F, when the dry plaster powder is mixed with water, it re-forms into gypsum. The setting of unmodified plaster starts about 10 minutes after mixing and is complete in about 45 minutes, if plaster or gypsum is heated above 266 °F, hemihydrate is formed, which will also re-form as gypsum if mixed with water. On heating to 180 °C, the nearly water-free form, called γ-anhydrite is produced, γ-Anhydrite reacts slowly with water to return to the dihydrate state, a property exploited in some commercial desiccants. On heating above 250 °C, the anhydrous form called β-anhydrite or dead burned plaster is formed. A large gypsum deposit at Montmartre in Paris led calcined gypsum to be known as plaster of Paris. Plasterers often use gypsum to simulate the appearance of surfaces of wood, stone, or metal, on movie, nowadays, theatrical plasterers often use expanded polystyrene, although the job title remains unchanged. Plaster of Paris can be used to impregnate gauze bandages to make a material called plaster bandages. It is used similarly to clay, as it is shaped when wet, yet sets into a resilient. This is the material that was used to make classic plaster orthopedic casts to protect limbs with broken bones, set Modroc is an early example of a composite material. The hydration of plaster of Paris relies on the reaction of water with the dehydrated or partially hydrated calcium sulfate present in the plaster, lime plaster is a mixture of calcium hydroxide and sand
Plaster of Paris
–
Early 19th Century plasterer at work - painting by
John Cranch (1751 - 1821).
Plaster of Paris
–
19th century
stucco plasterwork from
House of Borujerdies in
Kashan,
Iran.
Plaster of Paris
–
19th century, plasterwork in
Mazandaran,
Behshahr,
Iran.
Plaster of Paris
–
Plasterwork in
Pompeii (79 AD)
46.
Spar (mineralogy)
–
Spar is an old mining or mineralogy term used to refer to crystals that have readily discernible faces. A spar will easily break or cleave into rhomboidal, cubical, thus, the word spar in mineralogy has the same root as spear, by way of comparison to gypsum, as a common natural crystal forming in spearlike projections. Amongst miners the term today is frequently used alone to express any bright crystalline substance. Most frequently, spar describes easily cleaved, lightly colored nonmetallic minerals such as feldspar, baryte, the main source of barium, is also called heavy spar. Calcite often forms the dogtooth spar crystals found in vugs and caves, generally, a spar will form underwater, either in a phreatic zone, or below the water table, the essential place where most caves form, or in standing pools, as pool spar. If a cave floods and a pool forms, that submerges stalactites, mineral component ions in the water, mostly calcite or gypsum, but sometimes even halite, quartz, and fluorite, are deposited through the course of thousands of years, building up on each other. Sometimes, spar will form in the air due to solutions seeping out of the walls or through porous sediments. When grown in the air, it is made of gypsum or selenite. Sometimes it will form as small needles found in sediments, others spar can be found on the tips of gypsum chandeliers
Spar (mineralogy)
–
Dogtooth spar with fluorite from the Elmwood Mine in Tennessee
47.
Johann Friedrich Mayer (agriculturist)
–
Johann Friedrich Georg Hartmann Mayer was a German Reformed pastor and agricultural reformer, who is considered one of the most important writers on agriculture of his time. Mayer was born in Bad Mergentheim as son of an innkeeper and Schultheiß and his parents prepared him to become a minister at early age. He attended the Latin School in Weikersheim and the school in Öhringen. From 1741 to 1745 Mayer was Protestant pastor in Riedbach, which ended up in a dispute about defamation. In 1745 he moved to Kupferzell, near Crailsheim, where he was pastor until his death in 1798, there in the garden of his clergy house, Mayer conducted agricultural experiments and observed farm work on nearby farms. In 1768 he published his findings for the first time in his book, entitled Lehre vom Gyps als vorzueglich guten Dung zu allen Erd-Gewaechsen auf Aeckern und Wiesen, Hopfen- und Weinbergen. In this work he promoted the use of crushed gypsum as fertilization of fields and he further explained these operations in the 1774 publication M. Terentius Varro, von der Landwirtschaft. The agronomists of his time where so impressed by his work, in other writings, Mayer started describing the farmer relationships in natural farming and animal husbandry. In 1767 he started publishing the journal Beyträge und Abhandlungen zur Aufnahme der Land- und Hauswirthschaft, in addition to spreading his knowledge through books and magazines, Mayer traveled around and advised princes and peasants. He was invited to move to Vienna, both by Emperor Maria Theresia and Archbishop Christoph Anton Migazzi, but he declined and he advised the Hohenlohe peasants among other things about the cultivation of the still unknown potato. At first he only recommended the potato to feed livestock, and he also advocated free property for peasants. In the 18th Century the pressure upon agriculture had increased to feed the growing population. This work also suggested new ways of crop rotation, which broke with the traditional medieval three-field system from around the time of Charlemagne. Mayer among others presented plans for a new house, the so-called Pfarrer-Mayer-Häuser, in which the rural residential area. The barn, located on the floor, would heat the living room on the first floor. The introduction of fodder and the growing of apples in specific German regions date back to Mayers ideas. For better use of land Mayer suggested the farmers to plant fallow land with clover, thereby farmers gained additional fodder, which Mayer recommended to use in the stabling of cattle. A desirable side effect of stabling was the accumulation of manure that could be used as fertilizer on fields
Johann Friedrich Mayer (agriculturist)
–
Johann Friedrich Mayer (1719-1798)
Johann Friedrich Mayer (agriculturist)
–
Bad Mergentheim Marktplatz.
Johann Friedrich Mayer (agriculturist)
–
Map of the
Hohenlohe, Lehrbuch für die Land- und Haußwirthe, Plate I, 1773
Johann Friedrich Mayer (agriculturist)
–
Plate III, 1773-82.
48.
Hants County, Nova Scotia
–
Hants County is a county in the Canadian province of Nova Scotia. The county of Hants was established June 17,1781, on territory taken from Kings County and consisted of the townships of Windsor, Falmouth, the name Hants is an old abbreviation for the English county of Hampshire, from the Old English name Hantescire. In 1861, Hants County was divided for court sessional purposes into two districts named East Hants and West Hants, the Mikmaq are the aboriginal people who lived on these lands for centuries. They were clearly supporters of Abbe LeLoutres work in protecting Acadian and Mikmaq, within Hants County, they fought in the Battle at St. Croix on the St. Croix River. There is a history of missionary work in Hants County. There are still Mikmaq communities in Hants County such as Indian Brook 14, Nova Scotia and Shubenacadie 13, Shubenacadie is the oldest community in Hants County. The first Acadians to settle in present-day Hants County established farms at in the early 1680s, more Acadian villages soon followed spreading along the shores of the Piziquid and St. Croix rivers. One of these was at present day Windsor, Nova Scotia, with an expanding population the region by 1722 was split into two parishes. By the early 1700s Acadians migrated all along the shore of Hants County to the Shubenacadie River, one of the most prominent Acadians from this area was Noel Doiron who is the namesake of the community of Noel. With the founding of both Halifax and Fort Edward, there was an Acadian Exodus that involved an emigration of most of the Acadians from the Municipality of East Hants and they left British Nova Scotia for French occupied Prince Edward Island. The Expulsion of the Acadians from Hants County began at exactly the time as it happened at Grand-Pré. Fort Edward was one of four British forts in Acadia to imprison Acadians throughout the nine years of the expulsion, after the Acadians were removed from the area of present-day Hants County, New England Planters began to arrive and settle the vacated lands. They formed the townships of Windsor, Falmouth and Newport, one of the Planters of note during this period was Henry Alline who led the New Light revival of the Great Awakening in the region. Allines Newlight congregations were the progenitors of the Baptist movement in Canada, the next wave of immigration to Hants County was the Ulster Scots people who settled all along the Cobequid shore such as the OBriens in Noel, Nova Scotia and the Putnams in Maitland, Nova Scotia. During the American Revolution, Fort Edward played a pivotal role defending Halifax from a land attack. After the American Revolution, the Rawdon Township and Douglas Township were created for American Loyalists, the Douglas Township was settled by the 84th Regiment of Foot. The Rawdon Township was settled by loyalists from South Carolina whose lives had been saved in the Siege of Ninety-Six by Lord Rawdon, Windsor developed its gypsum deposits, usually selling it to American markets at Passamaquoddy Bay. Productive timber lands and tidal building sites made Hants County an important shipbuilding centre in the 19th century, loyalist merchant Abraham Cunard was an early shipbuilder in the county
Hants County, Nova Scotia
–
Monument to the Treaty of 1752,
Shubenacadie First Nation,
Nova Scotia
Hants County, Nova Scotia
–
Location of Hants County, Nova Scotia
Hants County, Nova Scotia
–
Fort Edward (built 1750). The oldest
blockhouse in North America.
Hants County, Nova Scotia
–
Hants County Township Map, 1879
49.
Brine
–
Brine is a solution of salt in water. In different contexts, brine may refer to salt solutions ranging from about 3. 5% up to about 26%, fahrenheit could reliably reproduce by freezing brine. By reference, seawater usually freezes at −2 °C, at 100 °C, saturated sodium chloride brine is about 28% salt by weight. At 0 °C, brine can only hold about 26% salt, the thermal conductivity of seawater is 0.6 W/mK at 25 °C. The majority of hydrogen produced through electrolysis is a side product in the production of chlorine. 2 NaCl +2 H2O →2 NaOH + H2 + Cl2 Brine is a fluid used in large refrigeration installations for the transport of thermal energy from place to place. The lowest freezing point obtainable for NaCl brine is −21.1 °C at 23. 3wt% NaCl and this is called the eutectic point. In lower temperatures, a solution can be used to de-ice or reduce freezing temperatures on roads. In cooking, brine is used for food brining and salting, in hydrology, brine is a form of salt water, namely, water with relatively high concentration of salt. Brine mining Saline water Brackish water
Brine
–
A NASA technician measures the concentration level of brine using a
hydrometer at a
salt evaporation pond in San Francisco.
China
Iran
Thailand
USA
Turkey
Spain
Mexico
Japan
Russia
Italy
India
Australia
Oman
Brazil
France
Canada
Saudi Arabia
Algeria
Germany
Argentina
Pakistan
United Kingdom
