Gypsum

The most common of the sulfate minerals, this mineral is found in marine evaporites, in caves, fumaroles, and in the oxidized zones of sulfide deposits. When formed as clear crystals, it is referred to as selenite. The fibrous variety is known as satin spar and also forms in "roses." It is used chiefly for the production of plaster of Paris, wallboard, and fertilizer. It is named in antiquity from the Greek, meaning “plaster.”

Mineral Photos courtesy of R.Weller/Cochise College