metamorphic
Greenstone
Greenschist / Greenstone (Epimetamorphic Rock)
AI-generated identification · may be incorrectHardness: 3.5-5.5 (variable); Color: Dull green, grayish-green, or dark green; Luster: Dull to waxy; Texture: Fine-grained, often massive or weakly foliated; Composition: Contains chlorite, epidote, or actinolite.
- Hardness
- 3
- Color
- Dull green, grayish-green, or dark green
- Luster
- Dull to waxy
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Physical properties
Hardness: 3.5-5.5 (variable); Color: Dull green, grayish-green, or dark green; Luster: Dull to waxy; Texture: Fine-grained, often massive or weakly foliated; Composition: Contains chlorite, epidote, or actinolite.
Formation & geological history
Formed through low-grade metamorphism (greenschist facies) of mafic igneous rocks like basalt or gabbro, usually under conditions of moderate temperature and pressure. Often associated with ancient volcanic arcs and mountain-building events.
Uses & applications
Used historically for stone tools (axes, adzes) due to its toughness. Today it is used as crushed stone for construction, road ballast, and sometimes in decorative landscaping or jewelry (when highly silicified).
Geological facts
Greenstone belts represent some of the oldest known rocks on Earth, some dating back over 3 billion years. They are significant in geology because they often host major gold and copper deposits.
Field identification & locations
Identify by its characteristic dull green hue that does not rub off. In the field, look for a dense, hard rock in areas with known volcanic-metamorphic history. It lacks the shiny mica flakes of higher-grade schists.
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