metamorphic
Greenstone
Greenschist / Meta-basalt
Hardness: 3.5-5.5 (variable); Color: Dull green, olive, or dark grayish-green; Luster: Waxy to dull (earthy); Structure: Fine-grained, often massive or weakly foliated; Specific Gravity: 2.85-3.0.
- Hardness
- 3
- Color
- Dull green, olive, or dark grayish-green
- Luster
- Waxy to dull (earthy)
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Physical properties
Hardness: 3.5-5.5 (variable); Color: Dull green, olive, or dark grayish-green; Luster: Waxy to dull (earthy); Structure: Fine-grained, often massive or weakly foliated; Specific Gravity: 2.85-3.0.
Formation & geological history
Formed through low-grade metamorphism (greenschist facies) of mafic igneous rocks like basalt or gabbro, under temperatures of 300-450°C and moderate pressure.
Uses & applications
Historically used for making stone tools; currently used as construction aggregate, decorative garden stone, and occasionally in jewelry as a 'river jade' lookalike.
Geological facts
The green color comes from minerals like chlorite, epidote, and actinolite replacing the original darker minerals in the basalt.
Field identification & locations
Look for a dull green hue that distinguishes it from common gray river rocks. It lacks the vitreous shine of true jade but is harder than common shale. Found in ancient mountain belts and subduction zones.
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