metamorphic
Greenstone
Metabasalt / Greenschist facies rock
Hardness of 5-6 on the Mohs scale, typically greenish in color due to minerals like chlorite, actinolite, and epidote, dull to sub-vitreous luster, massive or fine-grained crystal structure, indistinct cleavage, specific gravity around 2.7-3.0
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Physical properties
Hardness of 5-6 on the Mohs scale, typically greenish in color due to minerals like chlorite, actinolite, and epidote, dull to sub-vitreous luster, massive or fine-grained crystal structure, indistinct cleavage, specific gravity around 2.7-3.0
Formation & geological history
Formed through low-grade regional metamorphism of mafic igneous rocks such as basalt, gabbro, or diabase, typically occurring in ancient greenstone belts dating back to the Archean and Proterozoic eons.
Uses & applications
Used historically for stone axes and ornaments, currently utilized as crushed stone for aggregate in construction or as a decorative landscaping rock.
Geological facts
Greenstone belts contain some of the oldest rocks on Earth, providing crucial evidence about early plate tectonics and the conditions of the primordial Earth.
Field identification & locations
Easily identified in the field by its distinct green coloration and association with ancient shield areas. Commonly found in glaciated regions, riverbeds, and mountainous greenstone belts worldwide.
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