metamorphic
Greenstone
Metabasalt (Greenstone Facies)
Hardness: 6-7 (Mohs scale); Color: Dull green to dark forest green with white quartz/calcite veins; Luster: Sub-vitreous to earthy; Crystal structure: Massive/Microcrystalline; Specific Gravity: 2.85-2.95.
- Hardness
- 6-7 (Mohs scale)
- Luster
- Sub-vitreous to earthy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Dull green to dark forest green with white quartz/calcite veins; Luster: Sub-vitreous to earthy; Crystal structure: Massive/Microcrystalline; Specific Gravity: 2.85-2.95.
Formation & geological history
Formed through low-grade regional metamorphism of mafic igneous rocks (like basalt) at low temperatures and pressures. Often associated with Precambrian Shields and ancient mountain belts.
Uses & applications
Used as crushed stone for construction, architectural facade material, and historically for making stone tools (celts and axes) due to its toughness and lack of brittle cleavage.
Geological facts
Greenstone belts represent some of the oldest known rocks on Earth, dating back to the Archean Eon. Their green color comes from minerals like chlorite, epidote, and actinolite.
Field identification & locations
Look for a heavy, dense rock with a characteristic greenish hue that does not scratch easily; often features internal veining. Commonly found in the Appalachian Mountains, Lake Superior region, and Western Australia.
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