metamorphic
Epidosite
Epidosite (predominantly Epidote {Ca2Al2Fe3+Si3O12(OH)} and Quartz {SiO2})
Hardness: 6-7 on Mohs scale; Color: Pistachio-green to yellowish-green; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 3.3 to 3.5.
- Hardness
- 6-7 on Mohs scale
- Color
- Pistachio-green to yellowish-green
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Pistachio-green to yellowish-green; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 3.3 to 3.5.
Formation & geological history
Formed through the hydrothermal alteration or low-grade metamorphism of mafic igneous rocks (such as basalt) in environments like mid-ocean ridges or subduction zones. Can range from Precambrian to recent geological ages.
Uses & applications
Primarily used as a decorative stone or for gemstone carving. It has limited industrial use but is a significant indicator mineral for geologists studying metamorphic facies and hydrothermal ore deposits.
Geological facts
The characteristic 'pistachio' color is due to the presence of iron (Fe3+) in the crystal lattice. It is often found associated with chlorite and actinolite in 'greenschist' facies rocks.
Field identification & locations
Identify in the field by its distinct dull-green color and hardness; it will easily scratch glass but not quartz. Common in the Appalachian Mountains, the Swiss Alps, and areas with ophiolite complexes. Collectors look for its granular, sugary texture.
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