metamorphic
Tumbled serpentine (likely antigorite-rich)
Serpentine-group minerals, chiefly Mg₃Si₂O₅(OH)₄
AI-generated identification · may be incorrectGreen to cream, waxy to slightly vitreous luster, opaque to translucent, fine-grained and massive; Mohs hardness about 2.5–4, with poor cleavage and conchoidal-to-uneven fracture. The rounded surface indicates human tumbling/polishing.
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Physical properties
Green to cream, waxy to slightly vitreous luster, opaque to translucent, fine-grained and massive; Mohs hardness about 2.5–4, with poor cleavage and conchoidal-to-uneven fracture. The rounded surface indicates human tumbling/polishing.
Formation & geological history
Formed when ultramafic mantle rocks such as peridotite undergo hydration (serpentinization), commonly in oceanic crust and subduction zones; many deposits are Paleozoic to Mesozoic or younger. The image alone cannot establish an exact age or locality.
Uses & applications
Used as ornamental stone, carvings, beads, and decorative tile; historically used as a low-grade asbestos-associated stone, though fibrous varieties require caution. Common tumbled pieces have modest collector value.
Geological facts
The pale cream area may be altered serpentine, carbonate, or another adjacent mineral, so exact identification requires hardness, streak, density, and laboratory testing. Some serpentine rocks can contain chrysotile asbestos.
Field identification & locations
Common in California, Italy, New Zealand, Canada, Russia, and metamorphic ultramafic terrains worldwide; identify by greasy/waxy green appearance, low hardness, and association with dark ultramafic rock. Avoid sanding or cutting unknown specimens and wash hands after handling.
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