metamorphic
Greenschist
Greenschist (Chlorite-actinolite schist)
Hardness: 3.5-4.5 (Mohs scale); Color: Dark green to grey-green; Luster: Pearly to dull; Structure: Foliated, platy or elongated crystals; Cleavage: Excellent schistosic cleavage; Specific Gravity: 2.8-3.0
- Hardness
- 3
- Color
- Dark green to grey-green
- Luster
- Pearly to dull
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Physical properties
Hardness: 3.5-4.5 (Mohs scale); Color: Dark green to grey-green; Luster: Pearly to dull; Structure: Foliated, platy or elongated crystals; Cleavage: Excellent schistosic cleavage; Specific Gravity: 2.8-3.0
Formation & geological history
Formed via low-temperature, high-pressure regional metamorphism of mafic igneous rocks (like basalt) or similar sediments. Typically associated with subduction zones or mountain-building events.
Uses & applications
Primarily used as decorative stone in landscaping, facing stone for buildings, and occasionally as a base material in road construction or as crushed aggregate.
Geological facts
The green color characteristic of this rock comes from the presence of minerals like chlorite, epidote, and actinolite, which form under specific metamorphic conditions known as 'greenschist facies'.
Field identification & locations
Identify in the field by its distinct green hue and its tendency to split into thin, flat plates (foliation). Common in orogenic belts like the Appalachians or the Alps. Look for a soapy feel if chlorite content is high.
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