metamorphic
Greenschist
Chlorite schist
Hardness: 3.5-4.5 (Mohs scale); Color: green to grayish-green; Luster: Pearly to vitreous on foliation planes; Crystal structure: Monoclinic (chlorite components); Cleavage: Perfect basal cleavage in individual mineral grains; Foliated texture (schistosity).
- Hardness
- 3
- Color
- green to grayish-green
- Luster
- Pearly to vitreous on foliation planes
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Physical properties
Hardness: 3.5-4.5 (Mohs scale); Color: green to grayish-green; Luster: Pearly to vitreous on foliation planes; Crystal structure: Monoclinic (chlorite components); Cleavage: Perfect basal cleavage in individual mineral grains; Foliated texture (schistosity).
Formation & geological history
Formed through regional metamorphism of mafic igneous rocks (such as basalt) under low temperatures and moderate pressures (greenschist facies). This process typically occurs at convergent plate boundaries.
Uses & applications
Used primarily as decorative stone, for building facades, landscaping, and occasionally as a source of mineral pigments or industrial fillers.
Geological facts
The characteristic green color of greenschist is due to the presence of minerals like chlorite, epidote, and actinolite. It marks a specific intensity of metamorphism known to geologists as the 'Greenschist Facies'.
Field identification & locations
Identify in the field by its distinct green hue and its tendency to split into thin, flat plates (foliation). It is commonly found in mountain belts like the Appalachians, the Alps, and the Scottish Highlands. Collectors should look for signs of 'schistosity' where minerals have aligned perpendicular to pressure.
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