metamorphic
Greenstone
Greenschist (composed of chlorite, actinolite, and epidote)
Hardness: 3.5-5 (Mohs); Color: dull green to deep emerald green; Luster: dull to vitreous; Crystal structure: fine-grained/foliated; Specific Gravity: 2.85-3.0.
- Hardness
- 3
- Color
- dull green to deep emerald green
- Luster
- dull to vitreous
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Physical properties
Hardness: 3.5-5 (Mohs); Color: dull green to deep emerald green; Luster: dull to vitreous; Crystal structure: fine-grained/foliated; Specific Gravity: 2.85-3.0.
Formation & geological history
Formed through low-grade regional metamorphism of mafic igneous rocks (basalt/gabbro) at high pressure and low temperature, typically in subduction zones. Many are Archean or Proterozoic in age.
Uses & applications
Used as architectural stone, crushed stone for construction, and occasionally for decorative carvings or jewelry (often called 'New Zealand Jade' or 'Pounamu' in specific cultural contexts).
Geological facts
Greenstone belts are important historically because they often host major hydrothermal gold deposits. The green color comes specifically from the mineral chlorite.
Field identification & locations
Identify by its distinctive dull green hue and lack of visible large crystals. Common in ancient shield areas like Western Australia, Canada, and the Lake Superior region.
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