metamorphic
Greenschist
Chlorite Schist
Hardness: 2-3.5 on Mohs scale; Color: typically green, grayish-green, or dark green; Luster: Pearly to vitreous on foliation surfaces; Crystal Structure: Monoclinic (microscopic); Cleavage: Perfect basal cleavage leading to schistosity; Specific Gravity: 2.7-3.0.
- Hardness
- 2-3
- Color
- typically green, grayish-green, or dark green
- Luster
- Pearly to vitreous on foliation surfaces
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Physical properties
Hardness: 2-3.5 on Mohs scale; Color: typically green, grayish-green, or dark green; Luster: Pearly to vitreous on foliation surfaces; Crystal Structure: Monoclinic (microscopic); Cleavage: Perfect basal cleavage leading to schistosity; Specific Gravity: 2.7-3.0.
Formation & geological history
Formed through the regional metamorphism of mafic igneous rocks (like basalt) or sedimentary rocks under low-temperature (300-450°C) and moderate-pressure conditions. Characterized by the presence of green minerals like chlorite, epidote, and actinolite.
Uses & applications
Primarily used as a decorative stone in landscaping, crushed stone for road construction, and occasionally for high-end countertops or flagstones. Historically used for carvings and ornaments.
Geological facts
The 'greenschist facies' is a major classification in metamorphic petrology, representing a specific range of metamorphic conditions. Its distinctive green color comes from the mineral chlorite, which replaces heavier iron-magnesium minerals during metamorphism.
Field identification & locations
Identify by its platy, foliated (layered) texture and characteristic dull green color. It is easily scratched with a copper coin or knife. Commonly found in mountain belts and Precambrian shields.
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