metamorphic
Greenstone or Epidote-rich Metamorphic Rock
Chlorite/Epidote Schist or Greenstone
Hardness: 6-7 on Mohs scale; Color: Dull grayish-green to light olive green; Luster: Waxy to vitreous; Crystal Structure: Generally fine-grained or massive; Cleavage: Often indistinct in massive specimens; Specific Gravity: 2.8 - 3.4.
- Hardness
- 6-7 on Mohs scale
- Color
- Dull grayish-green to light olive green
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Dull grayish-green to light olive green; Luster: Waxy to vitreous; Crystal Structure: Generally fine-grained or massive; Cleavage: Often indistinct in massive specimens; Specific Gravity: 2.8 - 3.4.
Formation & geological history
Formed through low-grade regional or hydrothermal metamorphism of mafic igneous rocks (like basalt). During this process, minerals like chlorite, epidote, and actinolite replace original minerals, giving the rock its characteristic green hue. Commonly associated with ancient oceanic crust or volcanic arcs.
Uses & applications
Used as decorative stone, crushed stone for construction, and occasionally in jewelry as semi-precious beads or cabochons. Historically used for making tools due to its toughness.
Geological facts
Greenstone belts are some of the oldest geological formations on Earth, dating back billions of years to the Archean Eon. They are often targets for gold and copper mining operations.
Field identification & locations
Identify by its distinct greenish tint and high toughness. In the field, look for smooth, water-worn cobbles in riverbeds or coastal areas near former volcanic regions. It will often appear darker when wet.
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