mineral

Blue Anhydrite

Anhydrite (CaSO4)

Hardness: 3-3.5 (Mohs), Color: Pale blue to white, Luster: Vitreous to pearly on cleavage, Crystal Structure: Orthorhombic, Cleavage: Three perfect cleavages at 90 degrees, Specific Gravity: 2.97

Hardness: 3-3

Identified June 23, 2026More mineral →

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Physical properties

Hardness: 3-3.5 (Mohs), Color: Pale blue to white, Luster: Vitreous to pearly on cleavage, Crystal Structure: Orthorhombic, Cleavage: Three perfect cleavages at 90 degrees, Specific Gravity: 2.97

Formation & geological history

Formed as an evaporite mineral in sedimentary basins through the evaporation of seawater; often found in salt domes and marine evaporite deposits. Most gem-quality blue specimens are from the Mesozoic or Paleozoic eras.

Uses & applications

Used industrially in soil treatment, as a drying agent in plaster and cement, and in the production of sulfuric acid. The blue variety (known as Angelite) is used for decorative carvings and lapidary work.

Geological facts

The name Anhydrite comes from the Greek 'anydros' meaning 'without water,' distinguishing it from gypsum which has the same chemical composition but includes water. If exposed to water, it can hydrate and turn into gypsum.

Field identification & locations

Identify by its blocky cleavage and lack of reaction to acid. In the field, it is harder than gypsum but can still be scratched by a copper coin. Common locations include Peru, Mexico, and Germany.