Monohydrocalcite is a mineral that is a hydrous form of calcium carbonate, CaCO3·H2O. It was formerly also known by the name hydrocalcite, which is now discredited by the IMA. It is a trigonal mineral which is white when pure. Monohydrocalcite is not a common rock-forming mineral, but is frequently associated with other calcium and magnesium carbonate minerals, such as calcite, aragonite, lansfordite, and nesquehonite.
It has been reported as a significant component of the decomposition of ikaite in the towers of the Ikka Fjord, West Greenland. It is also noted for its bizarre occurrences, which include inside the otoliths of the tiger shark, the bladder of a guinea pig, the calcareous corpuscles of a cestode parasite, and the final stages of decomposition of the putrefying flesh of the giant saguaro cactus. These occurrences suggest a biochemical origin is possible.
1. ^ Swainson, I. P., The structure of monohydrocalcite and the phase composition of the beachrock deposits of Lake Butler and Lake Fellmongery, South Australia. American Mineralogist, Volume 93, 1014–1018, 2008 http://dx.doi.org/10.2138/am.2008.2825.
* Hull, H.; Turnbull, A. G. (1973). "A thermochemical study of monohydrocalcite.". Geochimica et Cosmochimica Acta 37: 685–694. doi:10.1016/0016-7037(73)90227-5. .