metamorphic
Greenstone
Metabasalt / Chlorite-actinolite-epidote schist
Hardness of 5-6 on the Mohs scale; typically olive-green, dark green, or grayish-green; dull to greasy luster; fine-grained crystal structure; poor to indistinct cleavage; specific gravity around 2.8-3.0.
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Physical properties
Hardness of 5-6 on the Mohs scale; typically olive-green, dark green, or grayish-green; dull to greasy luster; fine-grained crystal structure; poor to indistinct cleavage; specific gravity around 2.8-3.0.
Formation & geological history
Formed via low-grade regional metamorphism of mafic igneous rocks such as basalt, gabbro, or diabase under greenschist facies conditions, typically in ancient greenstone belts dating back to the Archean and Proterozoic eons.
Uses & applications
Used historically for making prehistoric stone axes and tools, in landscaping and decorative aggregate, and occasionally as a semi-precious gemstone or lapidary material for cabochons and carvings.
Geological facts
Greenstone belts represent some of the oldest surviving geological formations on Earth, often preserving the earliest evidence of plate tectonics and ancient oceanic crust.
Field identification & locations
Identified in the field by its distinct greenish coloration, dense feel, and fine-grained texture. Commonly found in glaciated regions, riverbeds, and ancient shield areas worldwide.
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