metamorphic
Greenschist / Meta-basalt
Greenschist (Metamorphosed Mafic Rock)
AI-generated identification · may be incorrectHardness: 5 - 6 on Mohs scale; Color: Dull greenish-gray to olive green with white or pale mineral flecks; Luster: Dull to weakly pearly or silky; Texture: Fine-grained to weakly schistose, water-worn and rounded; Specific Gravity: ~2.8 - 3.1
- Hardness
- 5 - 6 on Mohs scale
- Luster
- Dull to weakly pearly or silky
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Physical properties
Hardness: 5 - 6 on Mohs scale; Color: Dull greenish-gray to olive green with white or pale mineral flecks; Luster: Dull to weakly pearly or silky; Texture: Fine-grained to weakly schistose, water-worn and rounded; Specific Gravity: ~2.8 - 3.1
Formation & geological history
Formed via low-to-moderate grade regional metamorphism (greenschist facies) of mafic igneous rocks such as basalt or gabbro under moderate temperatures and pressures (~200–450°C). Often found transported and rounded in riverbeds or beaches.
Uses & applications
Commonly used in crushed stone aggregate, road construction, decorative gravel, landscaping, and occasionally carved into ornaments.
Geological facts
The characteristic greenish hue of greenschist arises from metamorphic minerals such as chlorite, epidote, and actinolite, replacing original dark minerals in volcanic basalt.
Field identification & locations
Identify by its distinctive dull green or olive cast, fine grain size, toughness, and occasional presence of white veinlets or speckles (quartz or calcite/feldspar). Found extensively in metamorphic belts, ophiolite suites, and glaciated river or coastal gravels.
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