mineral

Epidote

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

Hardness on Mohs scale is 6 to 7. Color is typically pistachio-green, yellowish-green, or blackish-green. Luster ranges from vitreous to resinous. Crystal structure is monoclinic, often forming prismatic crystals or granular aggregates. Cleavage is perfect in one direction. Specific gravity is 3.3 to 3.5.

Identified July 30, 2026More mineral →

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Physical properties

Formation & geological history

Forms primarily through regional and contact metamorphism of igneous rocks and impure limestones, as well as through hydrothermal alteration of minerals like plagioclase feldspar. Geological age varies widely depending on the host rock formation.

Uses & applications

Used primarily as mineral collector specimens. Occasionally cut into cabochons or beads for jewelry when found in massive forms with quartz (such as unakite).

Geological facts

Epidote is the namesake for the epidote group of minerals. The name comes from the Greek word 'epidosis', meaning 'increase', referring to the base of its crystal prism having one side longer than the other.

Field identification & locations

Easily identified in the field by its distinct pistachio-green color and monoclinic prismatic habit. Found worldwide, particularly in hydrothermal veins, alpine fissure veins, and altered metamorphic terranes.