metamorphic
Greenstone
Greenschist (Metamorphosed Mafic Rock)
Hardness: 3.5-5.0 (Mohs scale); Color: dull green to grayish-green; Luster: dull to slightly waxy; Crystal structure: fine-grained, often foliated or massive; Cleavage: poor; Specific gravity: 2.85-3.0.
- Hardness
- 3
- Color
- dull green to grayish-green
- Luster
- dull to slightly waxy
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Physical properties
Hardness: 3.5-5.0 (Mohs scale); Color: dull green to grayish-green; Luster: dull to slightly waxy; Crystal structure: fine-grained, often foliated or massive; Cleavage: poor; Specific gravity: 2.85-3.0.
Formation & geological history
Formed through low-grade metamorphism of mafic igneous rocks (such as basalt or gabbro) under relatively low temperature and pressure conditions, typically in subduction zones or orogenic belts. Most are Archean to Proterozoic in age.
Uses & applications
Used primarily as decorative stone, crushed stone for construction, and historically by indigenous people for making stone tools due to its toughness. Sometimes used for carvings or lapidary work.
Geological facts
The characteristic green color comes from minerals like chlorite, epidote, and actinolite. The 'Greenstone Belts' are some of the oldest known geological formations on Earth, frequently hosting major gold deposits.
Field identification & locations
Identify by its distinctive dull green hue and lack of visible large crystals. It is common in ancient shields like the Canadian Shield or Western Australia. It feels slightly heavier than common sandstone.
