metamorphic
Tumbled serpentine
Serpentinite; chiefly serpentine-group minerals (antigorite, lizardite, chrysotile), commonly with magnetite and carbonate
AI-generated identification · may be incorrectTypically olive-green to yellow-green, mottled, waxy to subvitreous luster, and fine-grained massive texture; hardness about 2.5–5.5 Mohs, with no obvious cleavage. The rounded, polished form is consistent with a tumbled stone.
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Physical properties
Typically olive-green to yellow-green, mottled, waxy to subvitreous luster, and fine-grained massive texture; hardness about 2.5–5.5 Mohs, with no obvious cleavage. The rounded, polished form is consistent with a tumbled stone.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite hydrate during low-temperature metamorphism; commonly associated with ancient oceanic crust and subduction zones, from Precambrian to modern settings.
Uses & applications
Used as an ornamental and lapidary stone, carvings, cabochons, and decorative aggregate; historically used as a low-grade ornamental “serpentine marble.” Chrysotile-bearing material should not be cut or abraded because of asbestos risk.
Geological facts
The mottled green-black pattern commonly reflects serpentine minerals with magnetite or chromite. Serpentinite is California’s state rock and often forms distinctive tectonic mélanges.
Field identification & locations
Identify by its green mottling, relatively low hardness, waxy feel, and occasional magnetic response; exact identification requires testing because similar patterns occur in altered basalt and jasper. Common localities include California, Italy, New Zealand, Canada, and the Appalachians.
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