Calcium carbonate monohydrate (CaCO3.H2O, CaHCO3(OH), monohydrocalcite) has been found in a wide variety of occurrences: Portland-cement reaction products1; calcareous encrustations in Lake Issyk-Kul, Kirgizstan2; otoliths (concretions in inner ear) of a tiger shark3; air-conditioning unit deposits4; in natural deposits (speleothems)5 by an evaporation-aerosol mechanism; a biochemical process6; lake deposits7; and in a guinea-pig bladder stone.8 It has also been synthesized by other investigators.913 Various impurities like polyphosphates, magnesium compounds, and some organic chemical additives, like sugar, and low temperature are known to favor the formation of this substance.
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