metamorphic
Greenschist
Greenschist facies metamorphic rock
Hardness: 3.5-5 on Mohs scale. Color: Dull dark green to grayish-green with dark weathered surface. Luster: Earthy, dull, to slightly silky. Structure: Fine-grained, foliated to semi-schistose texture. Specific gravity: ~2.8-3.0.
- Hardness
- 3
- Color
- Dull dark green to grayish-green with dark weathered surface
- Luster
- Earthy, dull, to slightly silky
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Physical properties
Hardness: 3.5-5 on Mohs scale. Color: Dull dark green to grayish-green with dark weathered surface. Luster: Earthy, dull, to slightly silky. Structure: Fine-grained, foliated to semi-schistose texture. Specific gravity: ~2.8-3.0.
Formation & geological history
Formed by low-grade regional metamorphism of mafic igneous rocks (such as basalt or gabbro) under low temperatures (200-400°C) and moderate pressures. Commonly composed of chlorite, epidote, actinolite, and albite.
Uses & applications
Historically used for stone tools, carving, and ballast. Currently used mainly as crushed stone in construction, road base, and decorative landscaping.
Geological facts
Greenschist gets its characteristic greenish color from green minerals like chlorite, actinolite, and epidote formed during low-temperature metamorphism. The process of its formation is called greenschist facies metamorphism.
Field identification & locations
Identified by its fine-grained texture, distinct greenish-grey tint on freshly broken surfaces, and soft to moderate hardness. Commonly found in ancient mountain belts, subduction zones, and greenstone belts worldwide.
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