metamorphic
Greenschist
Greenschist (Chlorite-Epidote-Actinolite Schist)
Hardness: 3.5-4.5 (Mohs scale); Color: Green, grayish-green, or olive; Luster: Pearly to dull; Crystal structure: Foliated/Schistose; Cleavage: Basal cleavage in micaceous minerals; Specific gravity: 2.8-3.0
- Hardness
- 3
- Color
- Green, grayish-green, or olive
- Luster
- Pearly to dull
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Physical properties
Hardness: 3.5-4.5 (Mohs scale); Color: Green, grayish-green, or olive; Luster: Pearly to dull; Crystal structure: Foliated/Schistose; Cleavage: Basal cleavage in micaceous minerals; Specific gravity: 2.8-3.0
Formation & geological history
Formed via regional metamorphism of mafic igneous rocks (like basalt) or similar sedimentary rocks under low-temperature, high-pressure conditions (greenschist facies). This process often occurs in mountain-building (orogenic) zones.
Uses & applications
Used primarily in construction as crushed stone, for architectural veneers, landscaping, and occasionally as a source of industrial minerals like talc or chlorite depending on specific composition.
Geological facts
The green color is primarily due to the presence of the minerals chlorite, epidote, and actinolite. The presence of greenschist often indicates the subduction or collision zones of ancient tectonic plates.
Field identification & locations
Identify by its characteristic green hue and fine-grained foliated (layered) texture that allows it to split into thin sheets. Commonly found in the Appalachian Mountains, the Alps, and the Scottish Highlands.
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