mineral

Epidote

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

Hardness: 6-7 Mohs; Color: Pistachio-green, yellow-green, or brownish-green; Luster: Vitreous to resinous; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific Gravity: 3.3 to 3.5.

Hardness: 6-7 Mohs
Color: Pistachio-green, yellow-green, or brownish-green
Luster: Vitreous to resinous

Identified April 5, 2026More mineral →

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Physical properties

Formation & geological history

Formed through regional metamorphism or hydrothermal alteration of igneous and sedimentary rocks. Common in greenschist facies and near contact zones where hot fluids interact with limestone or basalt.

Uses & applications

Used primarily as a minor gemstone (cabochons or beads) and as a mineral specimen for collectors. In industry, it can be used for geological dating (U-Pb dating of epidote crystals).

Geological facts

The name comes from the Greek 'epidosis' meaning 'increase,' referring to its crystal base being longer on one side. It is the namesake member of the epidote group, which includes zoisite and piemontite.

Field identification & locations

Identify in the field by its distinct 'pistachio green' color and its association with quartz and chlorite. It is commonly found in metamorphic mountain belts (e.g., Alps, Appalachians) and volcanic regions like Iceland or Unalaska (Unakite).