metamorphic
Greenschist (Greenstone)
Chlorite Schist / Greenschist Facies Rock
Hardness: 3.5-4.5 (Mohs); Color: Pale green to dark green with white/gray mottling; Luster: Dull to pearly; Crystal structure: Foliated or massive with platy mineral grains; Specific Gravity: 2.8–3.0.
- Hardness
- 3
- Color
- Pale green to dark green with white/gray mottling
- Luster
- Dull to pearly
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Physical properties
Hardness: 3.5-4.5 (Mohs); Color: Pale green to dark green with white/gray mottling; Luster: Dull to pearly; Crystal structure: Foliated or massive with platy mineral grains; Specific Gravity: 2.8–3.0.
Formation & geological history
Formed through low-grade regional metamorphism of mafic igneous rocks (like basalt) under low temperatures and high pressures. This process typically occurs in subduction zones or orogenic belts where tectonic plates collide.
Uses & applications
Used primarily as decorative stone, crushed stone for construction, and sometimes for sculpture. High-quality slabs are used for garden landscaping and flagstone.
Geological facts
The green color comes from the presence of green minerals like chlorite, epidote, and actinolite. It is a key indicator for geologists of the 'Greenschist Facies' metamorphic environment.
Field identification & locations
Identify in the field by its distinct grayish-green hue and sometimes a 'schistose' texture where it splits into flakey layers. It is commonly found in mountain ranges and accretionary prisms like the Appalachian Mountains or the Alps.
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