metamorphic
Greenstone
Metabasalt / Greenschist facies rock
Hardness: 5-7 Mohs; Color: Forest green to dark grey-green; Luster: Dull to sub-vitreous when wet; Structure: Fine-grained, sometimes foliated; Cleavage: Poor to none.
- Hardness
- 5-7 Mohs
- Color
- Forest green to dark grey-green
- Luster
- Dull to sub-vitreous when wet
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-7 Mohs; Color: Forest green to dark grey-green; Luster: Dull to sub-vitreous when wet; Structure: Fine-grained, sometimes foliated; Cleavage: Poor to none.
Formation & geological history
Formed through low-grade regional metamorphism of mafic igneous rocks (like basalt or gabbro) under low temperature and pressure, typically in ocean crust subduction zones.
Uses & applications
Historically used for making stone tools (celts and axes) due to its toughness; currently used as crushed stone for construction, decorative garden stone, and occasionally in jewelry.
Geological facts
The green color is primarily due to the presence of chlorite, actinolite, and epidote minerals. It was a prized material for prehistoric 'polished stone' tools across Europe and North America.
Field identification & locations
Identify by its distinct dark green hue and extreme toughness. Often found in orogenic (mountain-building) belts and as river-worn cobbles in glaciated or mountainous regions.
More like this
