Gypsum is a common mineral often found in sedimentary evaporite environments. It is one of the first minerals to form with the evaporation of seawater. Less commonly it forms in volcanic environments where limestone is altered by the high sulfur concentrations of the region. The major use of gypsum is as Plaster of Paris which is formed by grinding and heating the gypsum until most of the water is driven off (CaSO4 • 1/2 H2O). Later, when the water is re-added, it slowly resets into gypsum once again.
| CaSO4 • 2H2O |
|
| Sulfate |
|
| Monoclinic |
|
| 2/m |
|
| 2 |
|
| 2.32 |
|
| {010} perfect |
|
| Fibrous, conchoidal |
|
| Colorless, white, gray, tinted yellow, red or brown |
|
| White |
|
| Vitreous, pearly, silky |
|
| Transparent/translucent |
|
| Tabular, massive |
|
| Notable Localities: |
Chihuahua, Mexico; Jet, Oklahoma; Canada; France; Japan |
| Uses: |
Plaster of Paris, wallboard for construction |
| Halite, anhydrite, dolomite, calcite, sulfur, pyrite, quartz |
Specimens:
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