metamorphic
Greenstone
Protolith: Basaltic rock
Hardness: 6-7 on Mohs scale; Color: dark green to grayish-green; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic) or porphyritic; Specific gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- dark green to grayish-green
- Luster
- dull to earthy
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Physical properties
Hardness: 6-7 on Mohs scale; Color: dark green to grayish-green; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic) or porphyritic; Specific gravity: 2.8-3.0.
Formation & geological history
Formed through low-grade metamorphism of mafic igneous rocks (like basalt or gabbro) under low temperature and pressure conditions, often in subduction zones or mountain-building regions.
Uses & applications
Used as decorative stone, crushed stone for construction and road bases, and historically for making tools or weapons due to its toughness.
Geological facts
The characteristic green color comes from minerals like chlorite, epidote, and actinolite replacing the original minerals in the basalt.
Field identification & locations
Identify in the field by its distinct green hue and lack of foliation compared to schist. Commonly found in ancient mountain belts or ophiolite complexes.
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