metamorphic
Greenschist
Greenschist (composed mainly of chlorite, epidote, actinolite, and albite)
Hardness: 3.5-6 on the Mohs scale. Color: pale green to dark grey-green with brownish-orange oxidation iron staining streaks. Luster: dull to silky. Texture: fine-grained, foliated or schistose texture with wave-like mineral banding. Specific gravity: 2.8-3.2.
- Hardness
- 3
- Luster
- dull to silky
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Physical properties
Hardness: 3.5-6 on the Mohs scale. Color: pale green to dark grey-green with brownish-orange oxidation iron staining streaks. Luster: dull to silky. Texture: fine-grained, foliated or schistose texture with wave-like mineral banding. Specific gravity: 2.8-3.2.
Formation & geological history
Formed through low-grade regional metamorphism of mafic igneous rocks (such as basalt or gabbro) under relatively low temperatures (300-450°C) and moderate pressure. Often associated with subduction zones and ancient mountain-building events.
Uses & applications
Used historically and occasionally today as dimension stone, flagstone, decorative garden stone, and crushed stone for road base.
Geological facts
Greenschist gets its characteristic greenish color from green minerals like chlorite, epidote, and actinolite. Beach-tumbled specimens like this display fine sedimentary-like metamorphic layering enhanced by natural erosion.
Field identification & locations
Can be identified in the field by its distinct greenish tint, subtle mineral banding (foliation), and soft to medium hardness. Commonly found along rocky sea coasts, riverbeds, and mountainous regions with ancient metamorphic terranes.
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