metamorphic
Greenstone
Metamorphic Greenstone (Greenschist facies)
Hardness: 5-6 on the Mohs scale; Color: Shades of green, grey-green, or dark green; Luster: Dull to sub-greasy; Crystal structure: Microcrystalline to cryptocrystalline, often massive or foliated; Specific gravity: 2.7-3.0
- Hardness
- 5-6 on the Mohs scale
- Color
- Shades of green, grey-green, or dark green
- Luster
- Dull to sub-greasy
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Physical properties
Hardness: 5-6 on the Mohs scale; Color: Shades of green, grey-green, or dark green; Luster: Dull to sub-greasy; Crystal structure: Microcrystalline to cryptocrystalline, often massive or foliated; Specific gravity: 2.7-3.0
Formation & geological history
Formed by the low-grade regional metamorphism of mafic igneous rocks such as basalt, gabbro, or diabase under elevated pressures and temperatures, typically ranging from hundreds of millions to billions of years old.
Uses & applications
Used historically for stone axes and ornaments, commonly utilized today as crushed aggregate for construction, road metal, and sometimes as decorative landscaping stone.
Geological facts
Greenstone gets its characteristic color from green minerals such as chlorite, epidote, and actinolite that form during metamorphic alteration.
Field identification & locations
Found worldwide in ancient shields, orogenic belts, and river gravels. Identified by its characteristic greenish hue, lack of visible quartz, and toughness.
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