mineral

Epidote

Epidote, Ca₂(Al,Fe³⁺)₃(SiO₄)₃(OH); commonly occurring as an epidote-rich rock

AI-generated identification · may be incorrect

Typically pistachio-green to yellow-green, with a glassy to resinous luster and granular or prismatic crystals; Mohs hardness 6–7, monoclinic structure, poor cleavage, and specific gravity about 3.3–3.5. The pictured rounded specimen appears massive and fine-grained rather than a single crystal.

Identified August 25, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly during regional or contact metamorphism of calcium-rich rocks and in hydrothermal veins, often with quartz, feldspar, and amphibole. Most examples are Paleozoic or younger, although epidote-bearing rocks occur in much older metamorphic terranes.

Uses & applications

Used as a collector mineral and occasionally as a gemstone when transparent; epidote-rich rocks have limited ornamental or aggregate use but little major industrial value.

Geological facts

Its green color comes largely from iron³⁺ substitution for aluminum. Epidote commonly indicates altered, calcium-rich metamorphic or hydrothermal environments.

Field identification & locations

Identify by pistachio-green color, relatively high hardness, density, and association with quartz or metamorphic minerals; it does not fizz readily in dilute acid. Common localities include Austria, Pakistan, Norway, Mexico, and the United States.