metamorphic
Greenschist
Greenschist facies metamorphic rock
Hardness: 3.5 - 4.5. Color: Pale green to gray-green with some tan oxidation. Luster: Pearly to dull. Crystal structure: Typically foliated (schistose) with fine grains. Specific gravity: 2.8 - 3.0. Distinctive slaty/schistose cleavage.
- Hardness
- 3
- Color
- Pale green to gray-green with some tan oxidation
- Luster
- Pearly to dull
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Physical properties
Hardness: 3.5 - 4.5. Color: Pale green to gray-green with some tan oxidation. Luster: Pearly to dull. Crystal structure: Typically foliated (schistose) with fine grains. Specific gravity: 2.8 - 3.0. Distinctive slaty/schistose cleavage.
Formation & geological history
Formed through low-temperature, high-pressure regional metamorphism of mafic igneous rocks (like basalt) or similar sedimentary rocks. It typically forms at temperatures of 300 to 450 degrees Celsius.
Uses & applications
Used primarily as decorative stone, in landscaping, as garden ornaments, and historically as a local building stone in areas where it is abundant.
Geological facts
The 'green' in greenschist comes from minerals like chlorite, epidote, and actinolite. It is a key indicator of specific metamorphic conditions and defines the 'Greenschist Facies' in geology.
Field identification & locations
Identify in the field by its distinct greenish hue, platy or foliated layering, and relatively soft surface that can often be scratched by a copper coin or knife. Found in orogenic belts such as the Appalachians, Alps, and Scottish Highlands.
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