metamorphic
Greenstone
Metabasalt / Greenstone (low-grade metamorphic rock)
Hardness: 5-6 on the Mohs scale, Color: Various shades of green (due to chlorite, epidote, or actinolite), Luster: Dull to sub-vitreous, Crystal structure: Microcrystalline or fine-grained, Cleavage: None distinct.
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Physical properties
Hardness: 5-6 on the Mohs scale, Color: Various shades of green (due to chlorite, epidote, or actinolite), Luster: Dull to sub-vitreous, Crystal structure: Microcrystalline or fine-grained, Cleavage: None distinct.
Formation & geological history
Formed through low-grade regional metamorphism of mafic igneous rocks like basalt, diabase, or gabbro, typically in underwater environments or subduction zones.
Uses & applications
Historically used for making stone axes, weapons, and ornaments; occasionally used as decorative landscaping stone or in lapidary work.
Geological facts
Greenstone is heavily associated with ancient tectonic activity and oceanic crust alteration. The term encompasses several specific rock types like spilite and greenschist.
Field identification & locations
Identify by its distinctive greenish color and fine-grained texture. Commonly found in ancient shield areas, orogenic belts, and greenstone belts worldwide.
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