metamorphic
Greenstone
Metabasalt (Greenstone)
Hardness: 5-7 Mohs; Color: dark green to grayish-green; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic) or foliated; Specific gravity: approx. 2.9-3.3.
- Hardness
- 5-7 Mohs
- Color
- dark green to grayish-green
- Luster
- dull to earthy
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Physical properties
Hardness: 5-7 Mohs; Color: dark green to grayish-green; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic) or foliated; Specific gravity: approx. 2.9-3.3.
Formation & geological history
Formed from the low-grade metamorphism of mafic igneous rocks (like basalt or gabbro) under high pressure and low temperature conditions, often in subduction zones or mountain-building regions.
Uses & applications
Used historically for stone tools and weapons (axes); currently used as crushed stone for road construction, ornamental landscaping, and occasionally for lapidary work.
Geological facts
The characteristic green color comes from the presence of minerals like chlorite, actinolite, and epidote, which replace the original dark minerals in the parent rock.
Field identification & locations
Identify in the field by its distinct dull green hue and find it in tectonic suture zones or ancient volcanic terranes. It is often found as water-worn cobbles in riverbeds near mountainous regions.
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