Epidote
Species
Common · Ca₂Al₂(Fe³⁺)(Si₂O₇)(SiO₄)O(OH)
Calcium iron aluminium silicate common in low to medium grade metamorphic rocks. Its characteristic pistachio green colour results from ferric iron. Forms as a secondary mineral in the alteration of plagioclase feldspar.
Identity
- Formula
- Ca₂Al₂(Fe³⁺)(Si₂O₇)(SiO₄)O(OH)
- Chemical class
- Silicate
- Mineral group
- Tanzanite, Zoisite
- Also known as
- Pistacite (pistachio-green variety)
Crystallography
- Crystal system
- Monoclinic
- Habits
- Prismatic, Fibrous, Massive
- Fracture
- Uneven
Physical properties
- Mohs hardness
- 6.5
- Density
- 3.45 g/cm³
- Luster
- Vitreous
- Colors
- yellow-green, olive green, dark green, greenish black
- Streak
- colorless
- Transparency
- Transparent, Translucent
Geology
- Origins
- Metamorphic, Hydrothermal
- Host rocks
- Schist and gneiss, Marble
- Associated minerals
- Quartz, Calcite, Chlorite, Garnet
- Found in
- Skarn
- Geography
- Austria, Norway, Mexico, USA, Pakistan
Classification
- Rarity
- Common
- Gem quality
- No
Sources
- M. Pasero and others, IMA Commission on New Minerals, Nomenclature and Classification, The New IMA List of Minerals, updated September 2026. International Mineralogical Association (CNMNC), 2026.
- Epidote. Mindat.org (Hudson Institute of Mineralogy).
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Epidote. Mineral Data Publishing, Handbook of Mineralogy, 2001.
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