mineral

Epidote

{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)

Hardness: 6-7 on the Mohs scale. Color: Typically pistachio-green, yellowish-green, or brownish-green. Luster: Vitreous to resinous. Crystal Structure: Monoclinic, often forming prismatic crystals or granular masses. Cleavage: Perfect in one direction. Specific Gravity: 3.3 to 3.5.

Hardness: 6-7 on the Mohs scale
Luster: Vitreous to resinous

Identified March 16, 2026More mineral →

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Physical properties

Formation & geological history

Formed in low to medium-grade metamorphic rocks such as greenschist, or via hydrothermal alteration of igneous rocks (especially pyroxenes and amphiboles). It is commonly found in contact metamorphic zones.

Uses & applications

Occasional use as a gemstone (pistacite) when transparent; decorative carvings, mineral specimens for collectors, and an indicator mineral for geologists mapping metamorphic zones.

Geological facts

The name comes from the Greek word 'epidosis', meaning 'addition', referring to the crystal base being one side longer than the other. Its characteristic pistachio color is unique among common rock-forming minerals.

Field identification & locations

Identify in the field by its distinct 'pistachio' green color and high hardness (it cannot be scratched by a steel knife). Commonly found in the Swiss Alps, Norway, Alaska, and regions with significant tectonic metamorphism.