metamorphic
Greenschist (Greenstone)
Chlorite schist (primarily Chlorite-Epidote-Actinolite-Albite)
Hardness: 3.5-4.5 on Mohs scale; Color: Dull to bright green with dark phenocrysts; Luster: Pearly to vitreous; Crystal Structure: Schistose (foliated); Cleavage: Perfect in one direction due to micaceous minerals; Specific Gravity: 2.8-3.0
- Hardness
- 3
- Color
- Dull to bright green with dark phenocrysts
- Luster
- Pearly to vitreous
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Physical properties
Hardness: 3.5-4.5 on Mohs scale; Color: Dull to bright green with dark phenocrysts; Luster: Pearly to vitreous; Crystal Structure: Schistose (foliated); Cleavage: Perfect in one direction due to micaceous minerals; Specific Gravity: 2.8-3.0
Formation & geological history
Formed through regional metamorphism of mafic igneous rocks (such as basalt or gabbro) under low temperatures and high pressures, typically in subduction zones. Most deposits date from the Precambrian to Paleozoic eras.
Uses & applications
Commonly used in landscaping, as dimension stone for walls, and occasionally as an ornamental stone. In the past, it was used by indigenous cultures to carve tools and decorative objects.
Geological facts
Greenschist facies is a major classification in metamorphic petrology. The green color is derived from minerals like chlorite, epidote, and actinolite which form during the 'greenstone' alteration process.
Field identification & locations
Identify in the field by its distinct green hue, fine-grained texture, and the presence of dark mineral inclusions (phenocrysts). Commonly found in mountain belts and shield areas such as the Appalachian Mountains or the Canadian Shield.
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