metamorphic
Greenstone / Metabasalt
Metamorphosed Mafic Rock (Greenschist facies)
Hardness: 5-6.5 Mohs. Color: Dull green, grayish-green, or forest green. Luster: Dull to waxy when wet. Structure: Fine-grained, often massive or foliated. Specific Gravity: 2.8-3.1.
- Hardness
- 5-6
- Color
- Dull green, grayish-green, or forest green
- Luster
- Dull to waxy when wet
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6.5 Mohs. Color: Dull green, grayish-green, or forest green. Luster: Dull to waxy when wet. Structure: Fine-grained, often massive or foliated. Specific Gravity: 2.8-3.1.
Formation & geological history
Formed by the low-grade metamorphism of mafic igneous rocks like basalt or gabbro under low temperature and moderate pressure. Often found in ancient mountain belts and subduction zones.
Uses & applications
Used as construction aggregate, crushed stone for road beds, and occasionally as decorative stone or for lapidary work (jewelry). Ancient cultures used it for making stone tools (celts).
Geological facts
The green color comes from minerals like chlorite, epidote, and actinolite. The term 'Greenstone Belt' refers to large-scale geological formations that often contain significant gold deposits.
Field identification & locations
Identify by its characteristic dull green hue and lack of visible crystals compared to granite. Commonly found in riverbeds or coastal areas near ancient tectonic plate boundaries like the Pacific Northwest or Appalachians.
More like this
