metamorphic
Greenschist
Chlorite schist (Metamorphic rock dominated by chlorite, epidote, and actinolite)
Hardness: 3.5-4.5 on Mohs scale; Color: typically green to dark grey-green; Luster: Pearly to dull; Crystal structure: Foliated/Schistose; Cleavage: Excellent in one direction (slatiness); Specific Gravity: 2.8-3.0
- Hardness
- 3
- Color
- typically green to dark grey-green
- Luster
- Pearly to dull
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Physical properties
Hardness: 3.5-4.5 on Mohs scale; Color: typically green to dark grey-green; Luster: Pearly to dull; Crystal structure: Foliated/Schistose; Cleavage: Excellent in one direction (slatiness); Specific Gravity: 2.8-3.0
Formation & geological history
Formed through regional metamorphism of mafic igneous rocks (like basalt) under low-temperature, high-pressure conditions (greenschist facies). Common in Paleozoic and Precambrian mountain belts.
Uses & applications
Used primarily as decorative stone, crushed stone for road construction, and occasionally in landscape design or masonry. Historically used in craftwork or as a pigment source.
Geological facts
The 'green' color is specifically caused by minerals like chlorite, epidote, and actinolite. It identifies the 'Greenschist Facies,' a key set of pressure-temperature conditions that geologists use to map Earth's tectonic history.
Field identification & locations
Identify in the field by its distinct greenish hue and visible leaf-like layering (foliation) that allows it to split into thin sheets. Common in the Appalachian Mountains, Caledonian mountains, and alpine regions. Often found near convergent plate boundaries.
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