metamorphic
Greenschist
Greenschist (Chlorite Schist)
Hardness: 3.5-4.5 on Mohs scale; Color: typically dark green to grayish-green; Luster: dull to silky or pearly; Crystal structure: monoclinic (fine-grained); Cleavage: excellent orientation (schistosity); Specific gravity: 2.8-3.0.
- Hardness
- 3
- Color
- typically dark green to grayish-green
- Luster
- dull to silky or pearly
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Physical properties
Hardness: 3.5-4.5 on Mohs scale; Color: typically dark green to grayish-green; Luster: dull to silky or pearly; Crystal structure: monoclinic (fine-grained); Cleavage: excellent orientation (schistosity); Specific gravity: 2.8-3.0.
Formation & geological history
Formed through regional metamorphism of mafic igneous rocks (like basalt) under low-temperature (300-450°C) and moderate-pressure conditions. It typically dates from the Proterozoic to more recent orogenic events where plate subduction occurred.
Uses & applications
Used primarily as decorative stone, aquarium landscaping, and occasionally as minor construction aggregate or historical building material in specific regions.
Geological facts
The green color is primarily due to the presence of chlorite, epidote, or actinolite minerals. It is a hallmark of the 'Greenschist Facies' in metamorphic geology, representing the first major metamorphic changes to basaltic crust.
Field identification & locations
Identify in the field by its distinctive green hue and foliated (layered) texture that allows it to split into thin sheets. Commonly found in mountain belts and areas of ancient plate collisions like the Alps, Appalachians, or Pacific Coast Ranges.
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