Anhydrite
CHEMISTRY - CaSO4
CRYSTALLOGRAPHY - Orthorhombic, Dipyramidal
CRYSTAL GROWTH AND HABITS - Crystals are not common, Anhydrite is normally massive. It can be scaley, granular, fibrous or plumose. Crystals are equant, typically with large pinacoidal faces; also thick tabular.
COLOR AND OTHER OPTICAL PROPERTIES - Colorless to bluish or violet. It can also be white, rose, brownish or reddish. It is transparent to translucent.
HARDNESS - 3.5
SPECIFIC GRAVITY - 2.9 - 3.0
LUSTER - Vitreous to pearly, somewhat greasy.
STREAK - White
BREAKABILITY - Perfect {010} cleavage, {100} nearly perfect, {001} good. The fracture is uneven to splintery. Anhydrite is brittle.
OCCURRENCE - Anhydrite forms directly from the evaporation of seawater, and as a result is a common mineral in evaporite deposits.
ASSOCIATED MINERALS - Gypsum, Halite, Celestine, Dolomite, Calcite, Quartz.
MINERAL NAME - From the Greek meaning - without water.