metamorphic
Greenschist / Greenstone
Greenschist facies metabasite
Hardness: 3.5-5 (Mohs); Color: dull green to grey-green; Luster: dull to slightly silky; Crystal structure: foliated/schistose; Cleavage: poor; Specific gravity: 2.8-3.0.
- Hardness
- 3
- Color
- dull green to grey-green
- Luster
- dull to slightly silky
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Physical properties
Hardness: 3.5-5 (Mohs); Color: dull green to grey-green; Luster: dull to slightly silky; Crystal structure: foliated/schistose; Cleavage: poor; Specific gravity: 2.8-3.0.
Formation & geological history
Formed through regional metamorphism of mafic igneous rocks (like basalt) under low temperature and moderate pressure conditions. Usually associated with subduction zones or mountain building events.
Uses & applications
Used primarily as decorative stone, aquarium rocks, sometimes for stone tools in prehistoric times, and in crushed form for road construction.
Geological facts
The green color comes from minerals like chlorite, epidote, and actinolite. It is a key indicator for geologists to identify the specific thermodynamic history of a geological region.
Field identification & locations
Look for a dull green hue and a somewhat flaky or foliated texture. It is often found in riverbeds or beaches near ancient volcanic mountain ranges. It will not scratch glass easily.
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