metamorphic
Epidote
Epidote (Ca2(Al2,Fe3+)3(SiO4)3(OH))
Hardness: 6-7 Mohs; Color: Pistachio-green to yellowish-green; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 3.3-3.6
- Hardness
- 6-7 Mohs
- Color
- Pistachio-green to yellowish-green
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 Mohs; Color: Pistachio-green to yellowish-green; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 3.3-3.6
Formation & geological history
Formed during regional or contact metamorphism of igneous and sedimentary rocks. Common in greenschist facies and hydrothermally altered basaltic rocks. Generally formed during the Proterozoic to Cenozoic eras.
Uses & applications
Primarily collected as mineral specimens; occasionally used as a low-cost gemstone or industrial abrasive, though many specimens have more value to geological researchers.
Geological facts
The name 'epidote' comes from the Greek word 'epidosis' meaning 'addition', referring to the crystal sides being unequal in length. It is a common constituent of the rock Unakite.
Field identification & locations
Identified in the field by its distinct pistachio-green color and hardness. Often found in quartz veins or as an alteration product in granite or gabbro. Commonly found in locations like Norway, Austria, and various parts of the USA.
