metamorphic
Greenstone
Greenschist (composed of actinolite, chlorite, and epidote)
Hardness: 3.5-5 (Mohs); Color: dull green to deep emerald green; Luster: dull to vitreous; Crystal Structure: usually fine-grained or massive; Cleavage: poor; Specific Gravity: 2.8-3.3
- 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: usually fine-grained or massive; Cleavage: poor; Specific Gravity: 2.8-3.3
Formation & geological history
Formed through low-grade metamorphism of mafic igneous rocks (like basalt or gabbro) under low temperature and moderate pressure. Common in Precambrian orogenic belts.
Uses & applications
Historically used for making stone tools/axes; currently used as decorative gravel, in construction as crushed stone, and occasionally in jewelry as cabochons.
Geological facts
Many of the oldest known rock formations on Earth are found in greenstone belts, which contain vital information about the early development of the Earth's crust and precious metal deposits like gold.
Field identification & locations
Identify by its distinctive dull green hue and lack of foliation (if massive) or slight platy texture (if schisthose). Commonly found in ancient shield areas like the Canadian Shield or Western Australia.
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