metamorphic
Greenschist
Chlorite-actinolite schist
Hardness: 3.5 - 4.5. Color: Distinctive greenish hue due to chlorite, epidote, or actinolite. Luster: Pearly to sub-metallic on foliation planes. Crystal Structure: Schistose (foliated) texture with visible flaky minerals like mica or chlorite. Cleavage: Excellent slaty to schistose cleavage.
- Hardness
- 3
- Luster
- Pearly to sub-metallic on foliation planes
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Physical properties
Hardness: 3.5 - 4.5. Color: Distinctive greenish hue due to chlorite, epidote, or actinolite. Luster: Pearly to sub-metallic on foliation planes. Crystal Structure: Schistose (foliated) texture with visible flaky minerals like mica or chlorite. Cleavage: Excellent slaty to schistose cleavage.
Formation & geological history
Formed through low-grade regional metamorphism of mafic igneous rocks (like basalt) or volcanic sediment under low temperatures (300-450 °C) and moderate pressures. This usually occurs at convergent plate boundaries.
Uses & applications
Primarily used as decorative stone, in garden landscaping, or as a building fascia. Because of its flaky nature, it is not suitable for high-stress structural construction.
Geological facts
The 'Green' in greenschist comes from the presence of minerals like chlorite and epidote which only form under specific metamorphic conditions known as the 'greenschist facies'. It is a key indicator for geologists to understand the metamorphic history of a mountain range.
Field identification & locations
Identify by its greenish color and layered, foliated structure that allows it to split into thin sheets. It often feels slightly greasy or soapy due to chlorite content. Found commonly in the Appalachian Mountains, New Zealand, and the Alps.
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