metamorphic
Greenstone / Epidosite
Epidosite (primary minerals: Epidote and Quartz)
Hardness: 6-7 (Mohs); Color: Pistachio green to dark forest green with white/gray quartz; Luster: Vitreous to dull; Crystal structure: Monoclinic; Cleavage: One direction (perfect in epidote crystals, but indistinct in rock form).
- Hardness
- 6-7 (Mohs)
- Color
- Pistachio green to dark forest green with white/gray quartz
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs); Color: Pistachio green to dark forest green with white/gray quartz; Luster: Vitreous to dull; Crystal structure: Monoclinic; Cleavage: One direction (perfect in epidote crystals, but indistinct in rock form).
Formation & geological history
Formed through the regional or contact metamorphism of mafic igneous rocks (like basalt). The green color is primarily due to the mineral epidote, which forms from the hydrothermal alteration of calcium-rich minerals.
Uses & applications
Used as decorative stone, aquarium rocks, landscaping, and occasionally as a semi-precious gemstone for cabochons or beads. In construction, crushed greenstone is used for road base.
Geological facts
Greenstones often appear in ancient 'Greenstone Belts' which are some of the oldest geological formations on Earth, dating back to the Archean Eon. They are significant indicators of past tectonic activity.
Field identification & locations
Identify by its characteristic 'pistachio' green color and toughness. It is commonly found in mountain ranges or coastal areas where ancient oceanic crust has been uplifted and metamorphosed.
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