metamorphic
Greenstone or Epidote-rich rock
Epidote or Chlorite schist/greenstone
Hardness varies (Epidote is 6-7, chlorite is softer), green color, dull to slightly waxy luster, massive or slightly foliated structure depending on exact composition.
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Physical properties
Hardness varies (Epidote is 6-7, chlorite is softer), green color, dull to slightly waxy luster, massive or slightly foliated structure depending on exact composition.
Formation & geological history
Formed by low-grade regional metamorphism of basic igneous rocks (like basalt), where plagioclase and pyroxene alter to green minerals like chlorite, epidote, and actinolite.
Uses & applications
Commonly collected as a curiosity. Historically used by indigenous peoples for tools if dense enough. Sometimes polished as a minor gemstone (unakite if mixed with feldspar).
Geological facts
The term 'greenstone' is a broad field term for dark green altered basic igneous rocks.
Field identification & locations
Identify by its distinctive pistachio to dark green color and association with other metamorphic rocks. Common in ancient cratons and mountain belts.
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