metamorphic
Greenstone
Metamorphic Rock (Greenschist facies)
Hardness: 5-6 on the Mohs scale; Color: Greenish, grayish-green, or dark green due to chlorite and epidote; Luster: Dull to sub-vitreous; Crystal structure: Microcrystalline to fine-grained; Cleavage: Generally poor or indistinct.
- Hardness
- 5-6 on the Mohs scale
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 5-6 on the Mohs scale; Color: Greenish, grayish-green, or dark green due to chlorite and epidote; Luster: Dull to sub-vitreous; Crystal structure: Microcrystalline to fine-grained; Cleavage: Generally poor or indistinct.
Formation & geological history
Formed by the low-grade regional metamorphism of mafic igneous rocks such as basalt, gabbro, or diabase, typically under temperatures of 300-450 degrees Celsius and moderate pressures in ancient orogenic belts.
Uses & applications
Historically used by indigenous peoples for making stone axes and adzes; currently used occasionally as decorative landscaping stone or gravel.
Geological facts
Greenstone is heavily associated with ancient shield areas and is an important host rock for gold deposits in regions like the Abitibi greenstone belt in Canada.
Field identification & locations
Identify by its characteristic greenish hue and fine-grained texture. Common in ancient cratons, mountain-building roots, and glacial drift.
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