mineral

Epidote

Epidote (Ca2(Al,Fe)3(SiO4)3(OH))

Hardness: 6-7 on Mohs scale. Color: Pistachio green to dark green, blackish-green or yellowish-green. Luster: Vitreous (glassy) to pearly. Crystal Structure: Monoclinic, often found as prismatic crystals or granular masses. Cleavage: Perfect in one direction. Specific Gravity: 3.3 to 3.6.

Hardness: 6-7 on Mohs scale
Luster: Vitreous (glassy) to pearly

Identified January 13, 2026More mineral →

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Physical properties

Formation & geological history

Epidote is a common rock-forming mineral found in low-to-medium grade metamorphic rocks like greenschist, as well as in contact metamorphic zones. It also occurs in igneous rocks like basalt and granite through hydrothermal alteration of plagioclase feldspars. It is typically associated with the Proterozoic to Cenozoic eras depending on local tectonic activity.

Uses & applications

Used primarily as a minor gemstone for collectors and in jewelry (often as cabochons). It also serves as a diagnostic index mineral for geologists to identify pressure and temperature conditions during metamorphism (the 'Epidote-Amphibolite' facies).

Geological facts

The name comes from the Greek word 'epidosis,' meaning 'addition,' referring to the base of the crystal being longer on one side. It is the lead member of the epidote group, which includes zoisite and clinozoisite.

Field identification & locations

Identify in the field by its signature 'pistachio green' color and its high hardness (it will scratch glass but cannot be scratched by a steel knife). It is commonly found in the Alps, the Ural Mountains, and throughout the American Southwest and Northeast. Look for it in quartz veins or as green coatings on fractured rock surfaces.