metamorphic
Greenstone
Greenschist / Greenstone (Chlorite-Epidote facies)
Hardness: 5-6.5 (Mohs scale), Color: dull green to deep emerald green, Luster: dull to waxy, Structure: fine-grained to micro-crystalline, Cleavage: usually none/conchoidal fracture when massive, Specific Gravity: 2.8-3.3
- Hardness
- 5-6
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Physical properties
Hardness: 5-6.5 (Mohs scale), Color: dull green to deep emerald green, Luster: dull to waxy, Structure: fine-grained to micro-crystalline, Cleavage: usually none/conchoidal fracture when massive, Specific Gravity: 2.8-3.3
Formation & geological history
Formed through the low-grade metamorphism of mafic igneous rocks (like basalt or gabbro) under relatively low temperatures and pressures. Includes minerals like chlorite, actinolite, and epidote, often from the Archean or Proterozoic eons.
Uses & applications
Used historically for stone tools and weapons (axes). Today it is used as a construction aggregate, for landscaping, as a decorative building stone, and occasionally for lapidary work or polishing.
Geological facts
Greenstone belts are significant in geology because they often contain major gold, silver, and copper deposits. The green color is primarily due to the presence of chlorite and epidote minerals.
Field identification & locations
Identify by its distinctive dull green hue and fine-grained texture. It is harder than a fingernail and won't scratch easily. Common in ancient shield areas like the Abitibi in Canada, Western Australia, and parts of the Appalachian mountains.
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