Gypsum, crystal habit

The word g) sum comes from the Greek gyps, meaning burned mineral. There are several varieties of gypsum satin spar is a fine, soft, fibrous mineral alabaster is a more massive, fine-grained, and often banded form and selenite (. v.) a clear/ translucent form which shows good crystal habit. Extensive beds of selenite are worked in the Mediterranean basin, notably in southern Spain and Cyprus. 

Edinger, S.E. (1973) The growth of gypsum. An investigation of the factors which affect the size and growth rates of the habit faces of gypsum. Journal of Crystal Growth 18, 217-224. 

Van der Voort, E. Hartmann, P. (1991) The habit of gypsum and solvent interaction. Journal of Crystal Growth 112, 137-149. 

Gypsum forms monoclinic crystals that are tabular and diamond-shaped. Both habits are shown in Fig. 2. 

Selenite is a variety of gypsum with transparent or translucent, well formed crystals, with a rhombic tabular habit or sometimes twinned with swallowtail habit. Like g)tpsum, its chemical formula is CaS04.2H20. 

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