mineral
Epidote
Epidote (Ca2(Al,Fe)3(SiO4)3(OH))
AI-generated identification · may be incorrectHardness: 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
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Physical properties
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.
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.
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Other mineral specimens
Gneiss or Schist
Gneiss or Mica Schist with Garnet
Metamorphic
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Tumbled granite
Granite, a coarse-grained felsic intrusive igneous rock
igneous
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Granite
Granite (Phaneritic intrusive igneous rock)
igneous