Hydrocalcite (CaCO3 • H2O) and Nesquehonite (MgCO3 • 3H2O) in Carbonate Scales

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Science  12 Sep 1969:
Vol. 165, Issue 3898, pp. 1119-1121
DOI: 10.1126/science.165.3898.1119


Hydrocalcite (CaCO3 • H2O) with exactly one molecule of hydrate water is the main component of carbonate scales deposited from cold water in contact with air. When the magnesium content of the water is high, the hydrocalcite occurs together with MgCO3 • 3H2O (nesquehonite). From the conditions under which hydrocalcite is transformed into calcite and aragonite, it appears that in some cases aragonite in nature may be formed by way of an intermediary of CaCO3 • H2O.

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