Calcite recrystallization

Trace elements can be adsorbed on the surface of calcite, influencing their solubility in calcareous soils of arid and semi-arid zones. The carbonate bound fraction is the major solid-phase component for many trace elements (Cd, Pb, Zn, Ni and Cu) in arid and semi-arid soils, especially in newly contaminated soils (Table 5.3). In Israeli arid soils treated with metal nitrates, the carbonate bound fraction is the largest solid-phase component (60-80%, 50-60%, 40-60%, 30-40%, and 25-36% for Cd, Pb, Zn, Ni, and Cu respectively). Divalent metallic cations at low aqueous concentrations first associate with calcite via adsorption reactions. Then they may be incorporated into the calcite lattice as a co-precipitate by recrystallization (Franklin and Morse, 1983 Komicker et al., 1985 Davis et al., 1987 Zachara et al., 1988 Reeder and Prosky, 1986 Pingitore and... 

Zinc adsorption can occur via exchange of Zn2+ and Zn(OH)+ with surface-bound Ca2+ on calcite (Zachara et al., 1988). Zinc and Ni form surface complexes on calcite as hydrate until they are incorporated into the structure via recrystallization (Zachara et al., 1991). The selectivity of metal sorption on calcite is as follows Cd > Zn > Ni (Zachara et al., 1991). The easily reducible oxide bound metals are primarily from Mn oxides (Chao, 1972 Shuman, 1982 and 1985a). At pH > 6, Zn sorption on Mn oxide abruptly increases because of hydroxylation of the ions (Loganathan et al., 1977), and a high soil pH in arid soil may favor Zn sorption on Mn oxides due to a great... 

The simultaneous presence of the CaC03-reflections and of the CaO-reflections over a wide temperature range, and the persistence of certain calcite reflections point to topotaxy. This behaviour was generally observed during decomposition and recrystallization processes. The growth of the CaO crystallites with increasing temperature can be also seen in Fig. 61 (decrease of line broadening in the diffraction pattern). 

Chai B.H.T. (1974) Mass transfer of calcite during hydrothermal recrystallization. In Geochemical Transport and Kinetics, Vol. 634 (ed. A.W. Hofmann, B.J. Giletti, H.S. Yoder, and R.A. Yund), pp. 205-218. Garnegie Institution of Washington Publ. 

Curing of wetted coal ash results in carbona-tion to form calcite and possibly other metal carbonates. Calcite surfaces have been shown by Zachara et al. (1991) to preferentially sorb certain metals through adsorption followed by recrystallization (Zn, Co, Ni) or surface precipitation (Cd, Mn), but the total adsorption capacity of calcite for these metals is minor compared to their adsorption by other phases. 

Fig. 8. The effects of basic, neutral and acidic amino acids on the rate of recrystallization of aragonite to calcite the standard rate curve is given for comparison (after Jackson and Bischoff98 )...

Figure 2.13. Log of the rate of recrystallization plotted as a function of log (Q - 1) -1/2 log Z for artificial seawater systems in which calcite seeds are suspended in seawater, and the saturation state and coating thickness (Z) calculated from measurements of pH and total alkalinity. The solid line represents the data for the majority of experiments, whereas the dashed line is for a system containing a great deal of calcite in which the pH was measured in the sediment rather than in the supernatant seawater. (After Schoonmaker,1981.)...

The depth distribution of the Sr/Ca ratios of the recrystallized calcites in these sediments was calculated from the Sr2+/Ca2+ concentrations in the pore waters and appropriate values of the strontium distribution coefficient as a function of temperature from 5-25°C, where... 

Schoonmaker J.E. (1981) Magnesian calcite-seawater reactions solubility and recrystallization behavior. Ph.D. dissertation, Northwestern Univ., Evanston, IL. 

Videtich P.E. (1985) Electron microprobe study of Mg distribution in recent Mg calcites and recrystallized equivalents from the Pleistocene and Tertiary. J. Sediment. Petrol. 55, 421-429. 

Marble is formed from carbonate sediments, the most common of which is limestone. It is composed mostly of calcite. Pure marble is white, but it is easily stained by impurities such as iron oxide (red or brown) or manganese oxide (black). When the grains of calcite in limestone are exposed to heat and pressure, the mineral recrystallizes, forming a dense mass of inter-grown crystals. This makes marble stronger and slightly more dense than its parent rock. 

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