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Like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of marine organisms such as coral or foraminifera. These organisms secrete shells made of aragonite or calcite, and leave these shells behind when they die. Other carbonate grains comprising limestones are ooids, peloids, intraclasts, and extraclasts. Limestone often contains variable amounts of silica in the form of chert (chalcedony, flint, jasper). Limestone has numerous uses: as a building material, an essential component of concrete (Portland cement), as aggregate for the base of roads, as white pigment or filler in products such as toothpaste or paints, as a chemical feedstock for the production of lime, as a soil conditioner, or as a popular decorative addition to rock gardens.
Some limestones do not consist of grains at all, and are formed completely by the chemical precipitation of calcite or aragonite, i.e. travertine. Secondary calcite may be deposited by supersaturated meteoric waters (groundwater that precipitates the material in caves). This produces speleothems, such as stalagmites and stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular (oolite) appearance. The primary source of the calcite in limestone is most commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, building upon past generations. Limestone has numerous uses: as a building material, an essential component of concrete (Portland cement), as aggregate for the base of roads, as a chemical feedstock for the production of lime, as a soil conditioner, and for rock gardens.
In the US, aragonite in the form of stalactites and “cave flowers” is known from Carlsbad Caverns and other caves. Massive deposits of oolitic aragonite sand are found on the seabed in the Bahamas. ragonite is the high pressure polymorph of calcium carbonate. As such, it occurs in high pressure metamorphic rocks such as those formed at subduction zones. Aragonite forms naturally in almost all mollusk shells. The type location for aragonite is Molina de Aragón in the Province of Guadalajara in Castilla-La Mancha, Spain, for which it was named in 1797. The mineral is not named for the region of Aragon: Molina de Aragón is located in the historic region of Castile. Turquoise is insoluble in all but heated hydrochloric acid. Its streak is a pale bluish white and its fracture is conchoidal, leaving a waxy lustre. Despite its low hardness relative to other gems, turquoise takes a good polish. Turquoise may also be peppered with flecks of pyrite or interspersed with dark, spidery limonite veining.
Aragonite also forms in the ocean and in caves as inorganic precipitates called marine cements and speleothems, respectively. Aragonite is not uncommon in serpentinites where high Mg in pore solutions apparently inhibits calcite growth and promotes aragonite precipitation. Aragonite is metastable at the low pressures near the Earth’s surface and is thus commonly replaced by calcite in fossils. Aragonite older than the Carboniferous is essentially unknown. It can also be synthesized by adding a calcium chloride solution to a sodium carbonate solution. As a secondary mineral, turquoise forms by the action of percolating acidic aqueous solutions during the weathering and oxidation of preexisting minerals. For example, the copper may come from primary copper sulfides such as chalcopyrite or from the secondary carbonates malachite or azurite; the aluminium may derive from feldspar; and the phosphorus from apatite. Climate factors appear to play an important role as turquoise is typically found in arid regions, filling or encrusting cavities and fractures in typically highly altered volcanic rocks, often with associated limonite and other iron oxides.
In aquaria, aragonite is considered essential for the replication of reef conditions. Aragonite provides the materials necessary for much sea life and also keeps the pH of the water close to its natural level, to prevent the dissolution of biogenic calcium carbonate. Aragonite has been successfully tested for the removal of pollutants like zinc, cobalt and lead from contaminated wastewaters. Aragonite is thermodynamically unstable at standard temperature and pressure, and tends to alter to calcite on scales of 107 to 108 years. The mineral vaterite, also known as μ-CaCO3, is another phase of calcium carbonate that is metastable at ambient conditions typical of Earth’s surface, and decomposes even more readily than aragonite.
Labradorite a feldspar mineral, is an intermediate to calcic member of the plagioclase series. The streak is white, like most silicates. The refractive index ranges from 1.559 to 1.573 and twinning is common.
Like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of marine organisms such as coral or foraminifera. These organisms secrete shells made of aragonite or calcite, and leave these shells behind when they die. Other carbonate grains comprising limestones are ooids, peloids, intraclasts, and extraclasts. Limestone often contains variable amounts of silica in the form of chert (chalcedony, flint, jasper). Limestone has numerous uses: as a building material, an essential component of concrete (Portland cement), as aggregate for the base of roads, as white pigment or filler in products such as toothpaste or paints, as a chemical feedstock for the production of lime, as a soil conditioner, or as a popular decorative addition to rock gardens.
Some limestones do not consist of grains at all, and are formed completely by the chemical precipitation of calcite or aragonite, i.e. travertine. Secondary calcite may be deposited by supersaturated meteoric waters (groundwater that precipitates the material in caves). This produces speleothems, such as stalagmites and stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular (oolite) appearance. The primary source of the calcite in limestone is most commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, building upon past generations. Limestone has numerous uses: as a building material, an essential component of concrete (Portland cement), as aggregate for the base of roads, as a chemical feedstock for the production of lime, as a soil conditioner, and for rock gardens.
As with all plagioclase members, the crystal system is triclinic, and three directions of cleavage are present, two of which are nearly at right angles and are more obvious, being of good to perfect quality.
Minerals are classified by variety, species, series and group, in order of increasing generality. The basic level of definition is that of mineral species, each distinguished from the others by unique chemical and physical properties. For example, quartz is defined by its formula, SiO2, and a specific crystalline structure that distinguishes it from other minerals with the same chemical formula. When a range of composition between two minerals species exists, a mineral series is defined. The biotite series is represented by variable amounts of the endmembers phlogopite, siderophyllite, annite, and eastonite. Characteristically a cryptocrystalline mineral, turquoise almost never forms single crystals, and all of its properties are highly variable. X-ray diffraction testing shows its crystal system to be triclinic. With lower hardness comes lower specific gravity and greater porosity; these properties are dependent on grain size.
Chemistry and crystal structure together define a mineral. With a restriction to 32 point groups, minerals of different chemistry may have identical crystal structure. For example, halite, galena, and periclase all belong to the hexaoctahedral point group, as they have a similar stoichiometry between their different constituent elements. In contrast, polymorphs are groupings of minerals that share a chemical formula but have a different structure. For example, pyrite and marcasite are both iron sulfides; the former is isometric while the latter is orthorhombic. This polymorphism extends to all sulfides with the generic AX2 formula. Colour is as variable as the mineral’s other properties, ranging from white to a powder blue to a sky blue, and from a blue-green to a yellowish green. The blue is attributed to idiochromatic copper while the green may be the result of either iron impurities (replacing aluminium) or dehydration. A reading of 1.61–1.65 (birefringence 0.040, biaxial positive) has been taken from rare single crystals. An absorption spectrum may also be obtained with a hand-held spectroscope,
Malachite Individual crystals are rare but do occur as slender to acicular prisms. Malachite was extensively mined at the Great Orme mines in Britain 3,800 years ago using stone tools.
The major examples of these are quartz, the feldspars, the micas, the amphiboles, the pyroxenes, the olivines, and calcite; except for the last one, all of these minerals are silicates. Overall, around 150 minerals are considered particularly important, whether in terms of their abundance or aesthetic value in terms of collecting. Commercially valuable minerals and rocks are referred to as industrial minerals. For example, muscovite, a white mica, can be used for windows (referred to as isinglass), as a filler, or insulator. Ores are minerals that have a high concentration of a certain element. Malachite is also used for decorative purposes, such as in the Malachite Room in the Hermitage, which features a huge malachite vase, and the Malachite Room in Castillo de Chapultepec in Mexico City. “The Tazza”, a large malachite vase, one of the largest pieces of malachite in North America and a gift from Tsar Nicholas II, stands as the focal point in the center of the room of Linda Hall Library.
Crystal structure results from the geometric spatial arrangement of atoms in the internal structure of a mineral. This crystal structure is based on internal atomic or ionic arrangement that is often expressed in the geometric form that the crystal takes. Even when the mineral grains are too small to see, the underlying crystal structure is always periodic and can be determined by X-ray diffraction.Minerals are typically described by their symmetry content. Crystals are restricted to 32 point groups, which differ by symmetry. Groups are classified into broad categories, encompassing the six crystal families. The name Malachite may come from the Greek word malakee, or malache, signifying the resemblance of Mallow leaves, or from the Greek word malakos, meaning soft. Being a carbonate of copper, Malachite is sometimes intergrown with Azurite, forming Malachite-Azurite, or with Chrysocolla, forming Malachite-Chrysocolla.
Evidence indicates that the mineral has been mined and smelted to obtain copper at Timna Valley for over 3,000 years. Since then, malachite has been used as both an ornamental stone and as a gemstone.
Tranquillityite is silicate mineral mostly composed of iron, oxygen, silicon, zirconium and titanium with smaller fractions of yttrium and calcium. It is named after the Mare Tranquillitatis (Sea of Tranquility), the place on the Moon from which the rock samples in which it was found were brought during the Apollo 11 mission in 1969. Until its discovery in Australia in 2011, it was the last mineral brought from the Moon which was thought to be unique, with no terrestrial counterpart. In 1970, material scientists found a new unnamed Fe, Ti, Zr- silicate mineral containing rare-earths and Y in a lunar rock sample: #10047. The word turquoise dates to the 17th century and is derived from the French turquois for “Turkish” because the mineral was first brought to Europe through Turkey, from mines in the historical Khorasan Province of Persia.
Chalconatronite is a carbonate mineral and rare secondary copper mineral that contains copper, sodium, carbon, oxygen, and hydrogen. Chalconatronite is partially soluble in water, and only decomposes, although chalconatronite is soluble while cold, in dilute acids. The name comes from the mineral's compounds, copper ("chalcos" in Greek) and natron, naturally forming sodium carbonate. The mineral is thought to be formed by water carrying alkali carbonates (possibly from soil eacting with bronze. Similar minerals include malachite, azurite, and other copper carbonates. Most chalconatronite formed on bronze & silver have been treated with sodium sesquicarbonate or sodium cyanide. Pliny the Elder referred to the mineral as callais and the Aztecs knew it as chalchihuitl. The word turquoise dates to the 17th century and is derived from the French turquois for “Turkish” because the mineral was first brought to Europe through Turkey, from mines in the historical Khorasan Province of Persia.
Turquoise A blue-green mineral, a hydrated phosphate of copper & aluminium. It is rare and valuable in finer grades, prized as a gemstone and ornamental stone for thousands
The finest of turquoise reaches a maximum Mohs hardness of just under 6, or slightly more than window glass. Characteristically a cryptocrystalline mineral, turquoise almost never forms single crystals, and all of its properties are highly variable. X-ray diffraction testing shows its crystal system to be triclinic. With lower hardness comes lower specific gravity and greater porosity; these properties are dependent on grain size. Characteristically a cryptocrystalline mineral, turquoise almost never forms single crystals, and all of its properties are highly variable. X-ray diffraction testing shows its crystal system to be triclinic. With lower hardness comes lower specific gravity and greater porosity; these properties are dependent on grain size.
Pliny the Elder referred to the mineral as callais and the Aztecs knew it as chalchihuitl. The word turquoise dates to the 17th century and is derived from the French turquois for “Turkish” because the mineral was first brought to Europe through Turkey, from mines in the historical Khorasan Province of Persia. The name Malachite may come from the Greek word malakee, or malache, signifying the resemblance of Mallow leaves, or from the Greek word malakos, meaning soft. The finest of turquoise reaches a maximum Mohs hardness of just under 6, or slightly more than window glass. Characteristically a cryptocrystalline mineral, turquoise almost never forms single crystals, and all of its properties are highly variable. X-ray diffraction testing shows its crystal system to be triclinic. With lower hardness comes lower specific gravity and greater porosity; these properties are dependent on grain size.
Inspired by the hand lettering of 20th century book designer and calligrapher Oscar Ogg, Ogg captures the unique mix of calligraphic and typographic form achieved through his use of hand carved pen nibs, brushes, and white-out. The transitional stroke ductus of Ogg roman made for maximum legibility with an extremely compact word-shape, even when set at 8pt and below. In this vein, Ogg Text came to take on an unmistakably Dutch flavor.
Like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of marine organisms such as coral or foraminifera. These organisms secrete shells made of aragonite or calcite, and leave these shells behind when they die. Other carbonate grains comprising limestones are ooids, peloids, intraclasts, and extraclasts. Limestone often contains variable amounts of silica in the form of chert (chalcedony, flint, jasper). Limestone has numerous uses: as a building material, an essential component of concrete (Portland cement), as aggregate for the base of roads, as white pigment or filler in products such as toothpaste or paints, as a chemical feedstock for the production of lime, as a soil conditioner, or as a popular decorative addition to rock gardens. The primary source of the calcite in limestone is most commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, building upon past generations. Limestone has numerous uses: as a building material, an essential component of concrete (Portland cement), as aggregate for the base of roads, as a chemical feedstock for the production of lime, as a soil conditioner, and for rock gardens.
Some limestones do not consist of grains at all, and are formed completely by the chemical precipitation of calcite or aragonite, i.e. travertine. Secondary calcite may be deposited by supersaturated meteoric waters (groundwater that precipitates the material in caves). This produces speleothems, such as stalagmites and stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular (oolite) appearance. The primary source of the calcite in limestone is most commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, building upon past generations. Limestone has numerous uses: as a building material, an essential component of concrete (Portland cement), as aggregate for the base of roads, as a chemical feedstock for the production of lime, as a soil conditioner, and for rock gardens. The primary source of the calcite in limestone is most commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, building upon past generations. Limestone has numerous uses: as a building material, an essential component of concrete (Portland cement), as aggregate for the base of roads, as a chemical feedstock for the production of lime, as a soil conditioner, and for rock gardens.
In the US, aragonite in the form of stalactites and “cave flowers” is known from Carlsbad Caverns and other caves. Massive deposits of oolitic aragonite sand are found on the seabed in the Bahamas. ragonite is the high pressure polymorph of calcium carbonate. As such, it occurs in high pressure metamorphic rocks such as those formed at subduction zones. Aragonite forms naturally in almost all mollusk shells. The type location for aragonite is Molina de Aragón in the Province of Guadalajara in Castilla-La Mancha, Spain, for which it was named in 1797. The mineral is not named for the region of Aragon: Molina de Aragón is located in the historic region of Castile. Turquoise is insoluble in all but heated hydrochloric acid. Its streak is a pale bluish white and its fracture is conchoidal, leaving a waxy lustre. Despite its low hardness relative to other gems, turquoise takes a good polish. Turquoise may also be peppered with flecks of pyrite or interspersed with dark, spidery limonite veining.
Aragonite also forms in the ocean and in caves as inorganic precipitates called marine cements and speleothems, respectively. Aragonite is not uncommon in serpentinites where high Mg in pore solutions apparently inhibits calcite growth and promotes aragonite precipitation. Aragonite is metastable at the low pressures near the Earth’s surface and is thus commonly replaced by calcite in fossils. Aragonite older than the Carboniferous is essentially unknown. It can also be synthesized by adding a calcium chloride solution to a sodium carbonate solution. As a secondary mineral, turquoise forms by the action of percolating acidic aqueous solutions during the weathering and oxidation of preexisting minerals. For example, the copper may come from primary copper sulfides such as chalcopyrite or from the secondary carbonates malachite or azurite; the aluminium may derive from feldspar; and the phosphorus from apatite. Climate factors appear to play an important role as turquoise is typically found in arid regions, filling or encrusting cavities and fractures in typically highly altered volcanic rocks, often with associated limonite and other iron oxides.
In aquaria, aragonite is considered essential for the replication of reef conditions. Aragonite provides the materials necessary for much sea life and also keeps the pH of the water close to its natural level, to prevent the dissolution of biogenic calcium carbonate. Aragonite has been successfully tested for the removal of pollutants like zinc, cobalt and lead from contaminated wastewaters. Aragonite is thermodynamically unstable at standard temperature and pressure, and tends to alter to calcite on scales of 107 to 108 years. The mineral vaterite, also known as μ-CaCO3, is another phase of calcium carbonate that is metastable at ambient conditions typical of Earth’s surface, and decomposes even more readily than aragonite. For example, the copper may come from primary copper sulfides such as chalcopyrite or from the secondary carbonates malachite or azurite; the aluminium may derive from feldspar; and the phosphorus from apatite. Climate factors appear to play an important role as turquoise is typically found in arid regions, filling or encrusting cavities and fractures in typically highly altered volcanic rocks, often with associated limonite and other iron oxides.