(Science: chemical) a mineral consisting of the hydrous sulphate of lime (calcium). When calcined, it forms plaster of paris. Selenite is a transparent, crystalline variety; alabaster, a fine, white, massive variety.
Its chemical formula is CaSO4•2H2O.
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... rocks tell us that the hydrologic cycle was up and running and that the oceans were not entirely frozen at a very early date (around 3.8 Byr), gypsum crystals in ancient sediments indicate that the temperature could not have been too high since it is not stable above about 40°C. Occasional ...
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