metamorphic
Tumbled greenstone / serpentinite (probable)
Serpentinite, chiefly Mg-rich serpentine minerals (antigorite, lizardite, chrysotile), possibly mixed with chlorite, magnetite, or carbonate
AI-generated identification · may be incorrectOpaque blue-green to gray-green, mottled and earthy-to-waxy luster; typically Mohs 2.5–4, with no obvious cleavage and a fine-grained, massive texture. The rounded surface indicates natural or human tumbling/weathering; exact identification requires hardness, streak, and mineral testing.
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Physical properties
Opaque blue-green to gray-green, mottled and earthy-to-waxy luster; typically Mohs 2.5–4, with no obvious cleavage and a fine-grained, massive texture. The rounded surface indicates natural or human tumbling/weathering; exact identification requires hardness, streak, and mineral testing.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are hydrated during hydrothermal alteration, commonly in oceanic crust and ophiolite zones. Formation ages vary widely, from ancient Precambrian terrains to modern tectonic settings.
Uses & applications
Used as ornamental stone, carvings, lapidary material, and occasionally architectural facing; some greenstone varieties are made into jewelry. Common tumbled pieces generally have modest commercial value.
Geological facts
The photograph is consistent with serpentinite but cannot exclude nephrite jade, chlorite-rich rock, or weathered basalt without testing. Serpentinite may contain magnetite and can show weak magnetism; chrysotile-bearing material should not be cut or powdered.
Field identification & locations
Common in ophiolite belts, subduction complexes, and altered ultramafic terrains, including California, New Zealand, Italy, Canada, and the Appalachian region. Check for low hardness, a waxy feel, pale green streak, and possible magnetism; professional testing is needed to distinguish jade.
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