metamorphic
Greenstone
Metamorphic mafic rock (greenschist facies)
Hardness varies from 5 to 6 on the Mohs scale depending on mineral content; color ranges from dark green, grayish-green to yellowish-green; luster is dull to greasy; fine-grained crystal structure; lacks prominent cleavage.
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Physical properties
Hardness varies from 5 to 6 on the Mohs scale depending on mineral content; color ranges from dark green, grayish-green to yellowish-green; luster is dull to greasy; fine-grained crystal structure; lacks prominent cleavage.
Formation & geological history
Formed through low-grade regional metamorphism of mafic igneous rocks such as basalt, gabbro, or diabase, typically in subduction zones or oceanic crust environments during various geological eras.
Uses & applications
Used locally as decorative aggregate, in landscaping, and historically for making stone tools like adzes and axes due to its toughness.
Geological facts
Greenstone is well known in various cultures for being exceptionally tough and resistant to breaking, making it a primary material for prehistoric stone weapons and ceremonial tools.
Field identification & locations
Found globally in ancient shield areas, greenstone belts, and glaciated stream beds. Identified by its characteristic greenish hue and dense, interlocking fine-grained texture.
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