Calcium carbonate mineralogy

Bates N.R. and Brand U. (1990) Secular variation of calcium carbonate mineralogy An evaluation of odid and micrite chemistries. Geologishe Rundschau (in press). 

POLYMORPHISM. 1, A phenomenon in which a substance exhibits different forms. Dimorphic substances appear in two solid forms, whereas trimorphic exist in three, as sulfur., carbon, tin, silver iodide, and calcium carbonate. Polymorphism is usually restricted to the solid state, Polymorphs yield identical solutions and vapors (if vaporizable). The relation between them has been termed physical isomerism. See Allotropes under Chemical Elements, See also Mineralogy,... 

Morse J.W. (1983) The kinetics of calcium carbonate dissolution and precipitation. In Reviews in Mineralogy Carbonates - Mineralogy and Chemistry (ed. R. J. Reeder), pp. 227-264. Mineralogical Society of America. Bookcrafters, Inc., Chelse, MI. 

Sedimentary calcium carbonates are formed as the shells of marine plants and animals. Biologically produced CaCOs consists primarily of two minerals aragonite and calcite. Shallow-water carbonates, primarily corals and shells of benthic algae (e.g. Halimeda) are heterogeneous in their mineralogy and chemical composition but are composed mainly of aragonite and magnesium-rich calcite (see Morse and Mackenzie (1990) for a discussion). Carbonate tests of microscopic plants and animals, most of which hve in the surface ocean (there are also benthic animals that produce carbonate shells), are primarily made of the mineral calcite, which composes the bulk of the CaCOs... 

Tufa and travertine mineralogy tends to be dominated by low-Mg calcite, although there are some examples of aragonite and disordered dolomite in lacustrine tufas (e.g. Great Salt Lake, Utah Pedone and Dickson, 2000). The rare calcium carbonate hydrate known as ikaite has also been found in tufa (Buchardt et al., 2000). Vaterite, a rare anhydrous polymorph of calcium carbonate, has also been found to be co-precipitated with calcite in pools within a travertine barrage system at Huanglong, Sichuan, China (Lu et al., 2000). 

Rushdi, A.I., Pytkowicz, R.M., Suess, E. Chen, C.T. (1992) The effects of magnesium-to-calcium ratios in artificial seawater, at different ionic products, upon the induction time, and the mineralogy of calcium carbonate a laboratory study. GeoL Rundschau, 81, 571-578. 

Iceland spar (1771) n. Natural, transparent, double refracting, crystalhne form of calcium carbonate. Hibbard MJ (2001) Mineralogy. McGraw-Hill Co. Inc., New York. 

Sedimentary rocks are derived from weathered rock masses and deposited by the action of water or other means, or by the sedimentation of bioliths (mineral skeletons, shells, etc., of plants and animals) into layers, or, rarely, by chemical precipitation. Massive deposits of china clay or kaolin are found as a result of weathering, followed by movement and deposition. Limestone, the general term for natural calcium carbonate rocks, is the most abundant of the sedimentary rocks and is formed by the deposition of countless skeletons and shells. Gypsum and diatomaceous earths occur widely in sedimentary rocks. Sedimentary rocks are almost universally found in layered beds, which may have folded or otherwise been altered by subsequent geological events. Layers will differ from each other in texture, mineralogy and particle size. 

An example of a carbonate formation is one in which 95% of the bulk mineralogy is calcium carbonate (CaCOj). The remaining 5% represents other sandstone minerals partially filling or lining natural fractures, the principal flow channels in need of stimulation. Acid injection in such a... 

Figure 29.2 shows the mineralogic results of the calculation. Dolomite dissolves, since it is quite undersaturated in the waste fluid. The dissolution adds calcium, magnesium, and carbonate to solution. Calcite and brucite precipitate from these components, as observations from the wells indicated. The fluid reaches equilibrium with dolomite after about 11.6 cm3 of dolomite have dissolved per kg water. About 11 cm3 of calcite and brucite form during the reaction. Since calculation... 

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