Anhydrite
Naica, Mexico
The attractive crystal arrangement shown here is 15 cm high.
The specimen was obtained for the JMU collection from The Treasure Chest (formerly of Aberdeen, Maryland) in 1984.
Annhydrite CaSO4
Sulfates; calcium sulfate
Color and Luster: White, grayish, bluish, reddish to brick-red, pale lavender; vitreous, pearly on one cleavage; streak white to gray white
Hardness: 3-3.5
Cleavage: Good, three directions at 90°
Fracture: Uneven, brittle
Crystals: Orthorhombic; crystals rare; usually massive; also granular, compact, fibrous, cleavable
Anhydrite is an important sedimentary rock forming mineral occuring with dolomite, calcite, gypsum, and halite. It is deposited directly from high saline sea water, or by metamorphic dehydration of gypsum-bearing evaporites. Well developed crystals are uncommon.
Photo by Mary Sutherland
Descriptions taken from
The Audubon Society Field Guide to North American Rocks and Minerals