metamorphic
Greenstone
Metabasalt
Hardness: 6-7 (Mohs scale); Color: Dull forest green to dark olive; Luster: Matte to waxy; Crystal structure: Fine-grained, microcrystalline; Cleavage: Generally poor or none; Specific gravity: 2.8 - 3.2
- Hardness
- 6-7 (Mohs scale)
- Color
- Dull forest green to dark olive
- Luster
- Matte to waxy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Dull forest green to dark olive; Luster: Matte to waxy; Crystal structure: Fine-grained, microcrystalline; Cleavage: Generally poor or none; Specific gravity: 2.8 - 3.2
Formation & geological history
Formed through low-grade regional metamorphism of basaltic or similar igneous rocks. This process occurred in volcanic arcs and mountain-building regions over hundreds of millions of years.
Uses & applications
Used as decorative stone in landscaping, historic tool-making (celts and axes), and sometimes as a minor gemstone when containing chlorite or epidote patterns.
Geological facts
Greenstone belts are some of the oldest geological features on Earth, containing rocks that date back over 2.5 billion years to the Archean Eon.
Field identification & locations
Identify in the field by its characteristic green hue (due to chlorite or epidote) and its rounded, water-worn appearance in riverbeds. It is found in ancient geological shields such as the Canadian Shield and parts of Western Australia.
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