metamorphic
Greenstone / Serpentinite
Serpentine-group / Altered Mafic Rock
Hardness 2.5-5.5 on Mohs scale depending on specific alteration minerals, dull to waxy or vitreous luster, dark greenish-grey to olive-green color, microcrystalline to fibrous texture, waxy to soapy feel.
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Physical properties
Hardness 2.5-5.5 on Mohs scale depending on specific alteration minerals, dull to waxy or vitreous luster, dark greenish-grey to olive-green color, microcrystalline to fibrous texture, waxy to soapy feel.
Formation & geological history
Formed via low- to medium-grade regional or hydrothermal metamorphism of basalt, gabbro, or peridotite (often in subduction zones or oceanic crust environments).
Uses & applications
Used historically for carving decorative objects, tools, dimension stone, and as aggregate material in construction; collected as a decorative beach pebble.
Geological facts
Greenstone is a broad term used for altered, greenish, fine-grained igneous or metamorphic rocks that often form ancient greenstone belts, which can host important ore deposits like gold.
Field identification & locations
Can be identified in the field by its distinct greenish-grey coloration, smooth stream- or ocean-worn rounded shape, soft waxy feel, and fine-grained texture. Commonly found along beaches, rivers, and exposed metamorphic terranes in coastal areas.
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