metamorphic
Greenstone
Greenschist
Hardness: 3.5-5 (Mohs scale), Color: dull green to deep emerald with dark streaks, Luster: waxy to greasy when polished, Crystal structure: microcrystalline/foliated, Cleavage: poor, Specific gravity: 2.7–3.0
- Hardness
- 3
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Physical properties
Hardness: 3.5-5 (Mohs scale), Color: dull green to deep emerald with dark streaks, Luster: waxy to greasy when polished, Crystal structure: microcrystalline/foliated, Cleavage: poor, Specific gravity: 2.7–3.0
Formation & geological history
Formed through the low-grade metamorphism of mafic igneous rocks (like basalt) under high pressure and low temperatures, typically in subduction zones during the Paleozoic or Mesozoic eras.
Uses & applications
Used historically for stone tools (celts and axes), modernly used for lapidary work, decorative garden stones, and minor architectural veneers.
Geological facts
The 'green' color is primarily due to the presence of minerals like chlorite, actinolite, and epidote. It was highly prized by Neolithic cultures for its toughness.
Field identification & locations
Identify by its characteristic greenish hue even when dry and its tendency to feel smoother or 'softer' than quartz-rich stones. Commonly found in riverbeds in orogenic (mountain-building) belts like the Pacific Northwest or Appalachians.
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