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Anhydrite
Main Deposits
Abundant in Germany near Hanover, Great Britain, France, Austria, USA, India, Russia, Chile.
Description and Characteristics
Anhydrite is an anhydrous calcium sulfate found primarily in evaporitic sedimentary rock deposits; it forms through the dehydration of gypsum or the direct precipitation of saline solutions under high-temperature conditions. It belongs to the orthorhombic crystal system and typically occurs as granular or fibrous masses that are white, gray, or bluish in color; it is a mineral of great industrial and geological importance, characterized by its ability to absorb water, thereby increasing its volume and transforming into gypsum, which causes significant changes in the structure of the strata where it is found.
| Chemical Formula | $$CaSO₄$$ |
|---|---|
| Luster | Vitreous to pearly |
| Streak | White |
| Fracture | Irregular to splintery |
| Cleavage | Perfect |
| Hardness | 3,5 Mohs |
| Crystal System | Orthorhombic |
Did you know...?
The name comes from the Greek word *anhydros*, meaning “without water,” highlighting its main difference from gypsum. In mining and construction, it is a mineral that requires caution, since if it hydrates inside a mountain or structure, its expansion can exert massive pressure capable of lifting tunnels or buildings.