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Gypsum is a very common mineral, with thick and extensive beds association with sedimentary rocks. The largest deposits known occur in strata from the Permian age. Gypsum is deposited in lake and sea water, as well as in hot springs and from volcanic vapors, and sulfate solutions in veins.
The word gypsum is derived from the Greek meaning 'to cook', in reference to the burnt or calcined mineral. Because the gypsum from the quarries of the Montmartre district of Paris has long furnished burnt gypsum used for various purposes this material has been called plaster of Paris.
Crystallographic system | Monoclinic |
Colours | Colourless to white and grey though it may be tinted red, yellow, blue, brown, etc. by impurities. |
Lustre | Vitreous to silky or pearly lustre |
Hardness | 1.5–2 |
Refractive index | 1.522( average) |
Specific gravity | 2.31–2.33 |
Cleavage | 2 good (66° and 114°) |
Twinning | Very common |
Pleochroism | Colourless |
See also: List of minerals
Gypsum is also a place name in the State of Ohio in the United States of America. See Gypsum, Ohio[?].
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