Minerals calcite

Texture. All limestones are crystalline, but there is tremendous variance in the size, uniformity, and arrangement of their crystal lattices. The crystals of the minerals calcite, magnesite, and dolomite are rhombohedral those of aragonite are orthorhombic. The crystals of chalk and of most quick and hydrated limes are so minute that these products appear amorphous, but high powered microscopy proves them to be cryptocrystalline. Hydrated lime is invariably a white, fluffy powder of micrometer and submicrometer particle size. Commercial quicklime is used in lump, pebble, ground, and pulverized forms. 

The veins are composed mostly of quartz and a small amount of sulfide minerals (pyrite, pyrrhotite, arsenopyrite, chalcopyrite, sphalerite, and galena), carbonate minerals (calcite, dolomite) and gold, and include breccias of the host rocks with carbonaceous matters. Layering by carbonaceous matters has been occasionally observed in the veins. Banding structure, wall rock alteration and an evidence of boiling of fluids that are commonly observed in epithermal veins have not been usually found. 

Figure 8.16 (a) IR and (b) Raman spectra for the mineral calcite, CaC03. The estimated density of vibrational states is given in (c) while the deconvolution of the total heat capacity into contributions from the acoustic and internal optic modes as well as from the optic continuum is given in (d). 

A large portion of the REOs are produced from monazite- and bastnaesite-containing ores. In the majority of cases, bastnaesite and monazite ores are relatively complex and contain gangue minerals (calcite, barite, fluorite and apatite) with similar flotation properties as the monazite and bastnaesite. 

In the present-day ocean, about half of the PIC exported to oceanic sediments consists of the remains of foraminiferans. These microorganisms are protozoans. They are widespread in the marine environment with some species having a pelagic lifestyle and others benthic. As shown in Figure 15.1a, their calcareous structures have the appearance of a chambered snail shell and are composed of the mineral calcite. Since this hard part is covered by tissue, it is technically a type of skeleton. These detrital remains are referred to as tests or forams. Among the present-day and extinct species of foraminiferans, considerable variation exists in the size, shape, and density of their tests. 

The carbonate (C03 ) ion can combine with divalent cations to form solid minerals, calcite and aragonite being the most common... 

The simulations indicate precipitation of the carbonate minerals calcite (CaC03), dolomite... 

Geothermal aquifer waters are close to saturation with some scale-forming minerals (calcite, pyrite) but undersaturated with others (amorphous silica, amorphous metallic sulphides). Only the slightest degassing suffices to produce calcite oversaturated water. By contrast, extensive cooling may be required to produce amorphous-silica oversaturation. As solubility constants are... 

Limestone consists mainly of the mineral calcite, CaC03. The carbonate content of 0.541 3 g of powdered limestone was measured by suspending the powder in water, adding 10.00 mL of 1.396 M HC1, and heating to dissolve the solid and expel COz ... 

Ca2+ is the most common cation in rivers and lakes. It comes from dissolution of the mineral calcite by the action of C02 to produce 2 moles of HCO j for each mole of Ca2+ ... 

The magnetization is negative and the materials have a pr-value of approximately 0.99995. Diamagnetism can only exist in an external field and among the materials which exhibit this phenomenon are Cd, Cu, Ag, Sn and A1203, as well as the minerals calcite CaC03 and fluorite CaF2. 

Limestone is mostly made up of the mineral calcite, or calcium carbonate (CaC03). As the calcium carbonate rock dissolves in the slightly acidic water, spaces and even caves develop underground. If carbonic acid dissolves all the way through the rock and into a cave below the Earth s surface, the resulting solution contains calcium hydrogen carbonate (calcium bicarbonate). 

Limestone is composed of calcium carbonate (CaC03) in the form of the mineral calcite (Figure 13.2). Chalk and marble are also made of calcite which is the second most abundant mineral in the Earth s crust after the different types of silicates (which include clay, granite and sandstone). 

Calcium carbonate (CaC03) occurs naturally as calcite (density 2.7), a widely distributed mineral. Calcite is a common constituent of sedimentary rocks, as a vein mineral, and as deposits from hot springs and in caves as stalactites and stalagmites. Calcite is white or colorless through shades of gray, red, yellow, green, blue, violet, brown, or even black when charged with impurities streaked, white transparent to opaque. It may occasionally show phosphorescence or fluorescence. 

In the oceans half of the DIC riverine input accumulated in nearshore (coastal zones, oceanic banks and atolls, shelves) and open ocean (hemipelagic and pelagic) sediments as calcium and magnesium carbonate minerals (calcite, aragonite, magnesian calcite), and half eventually returned to the atmosphere owing to precipitation (e.g.) ... 

The minerals calcite and aragonite are polymorphs of calcium carbonate. Calcite is the more stable of the two, and aragonite is most often seen in objects made of speleothems, the rocks formed in solution caverns. Aragonite is also an important constituent in many materials of organic origin, such as mollusk shells and the outer skeletons of sand dollars and coral. Calcite is the major component of the rocks limestone and marble, and as such is found in collections as sculpture, building stone, in mosaics, and in inlay or in tarsia. 

A), Sr2+ (1.13 A) and Pb2+ (1.19 A) are well within the range of each other. The minerals calcite, fluorite and apatite belong to this group. 

The most important compound of calcium is calcium carbonate, CaCOa. This substance occurs in beautiful colorless crystals as the mineral calcite (Fig. 9-2). Marble is a micro-crystalline form of calcium carbonate, and liifiestone is a rock composed mainly of this substance. Calcium carbonate is the principal constituent also of... 

As in most parts of today s deep ocean the concentrations of Ca and of CO are nearly constant with water depth, profiles of CaCOs content with depth reflect mainly the increase in the solubility of the mineral calcite with pressure (see Figure 2). This increase occurs because the volume occupied by the Ca and ions... 

World annual production of natural diamonds, the cubic form of carbon, is about 110 million carats (1 carat = 200 mg). Almost all is derived from kimberlite or its weathered remnants, but Australian production is from the Argyle mine, at which the host rock is lamproite. Kimberlites are olivine- and volatUe-rich potassic ultrabasic rocks of variable geological age that typically form near-vertical carrot-shaped pipes intmded into Archean cratons. The volatile-rich component is predominantly CO2 in the carbonate minerals calcite and dolomite, and the texture is characteristically inequigranular, with large grains (macrocrysts), usually of olivine [Mg2Si04], in a fine-grained, olivine-rich matrix. 

The phenomenon of polymorphism was noted by Martin Heinrich Klaproth °i in 1798, when he proposed that the minerals calcite and aragonite must have the same chemical composition, CaCOa. Calcite forms a rhombohedral uniaxial crystal and is the stable form under normal conditions, with a density of 2.71 g/ml. Its metastable polymorph, aragonite, is an orthorhombic biaxial crystal with a density of 2.94 g/ml. This work was continued by Louis Jacques Thernard, Jean Baptiste Biot, and Eilhard Mitscherlich. Mitscherlich, for example, reported on it in his studies of phosphates and arsenates. The transition from calcite to aragonite has been studied at different pressures. ... 

Carbonate minerals. Calcite (left) and aragonite (middle) are both CaCOs, and smithsonite (right) isZnCOs. 

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