metamorphic
Green Schist
Greenschist (composed primarily of Chlorite, Actinolite, and Epidote)
Hardness: 3.5-4.5 (Mohs scale); Color: distinct grayish-green to emerald green; Luster: vitreous to pearly; Crystal structure: Monoclinic (foliated); Cleavage: perfect in one direction along foliation; Specific gravity: 2.8-3.3.
- Hardness
- 3
- Color
- distinct grayish-green to emerald green
- Luster
- vitreous to pearly
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Physical properties
Hardness: 3.5-4.5 (Mohs scale); Color: distinct grayish-green to emerald green; Luster: vitreous to pearly; Crystal structure: Monoclinic (foliated); Cleavage: perfect in one direction along foliation; Specific gravity: 2.8-3.3.
Formation & geological history
Formed through low-temperature, moderate-pressure regional metamorphism (greenschist facies) of mafic igneous rocks (like basalt) or sedimentary rocks. This typically occurs at depths of 10-25 km during mountain-building events (orogeny).
Uses & applications
Used primarily as decorative stone, in landscaping, and architectural veneers. Historically used for making tools and ornaments when harder varieties were available. It is also an important geological indicator of tectonic history.
Geological facts
The green color is primarily due to the presence of Chlorite. It marks a specific metamorphic 'grade' that geologists use to map the pressure and temperature conditions a mountain range has endured over millions of years.
Field identification & locations
Identify in the field by its distinct green hue and strongly foliated (layered/platy) texture that often splits into thin sheets. Common in orogenic belts like the Appalachians, Alps, and Scottish Highlands. Collectors should look for fine-grained, shimmering surfaces.
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