metamorphic
Tumbled serpentine
Serpentinite; chiefly antigorite, lizardite, or chrysotile Mg₃Si₂O₅(OH)₄, with possible magnetite and carbonate
AI-generated identification · may be incorrectTypically olive-green to brown with mottled, waxy or greasy luster; Mohs hardness about 2.5–4, white streak, poor cleavage, and fine-grained massive texture. The rounded, polished appearance indicates tumbling rather than natural crystal faces.
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Physical properties
Typically olive-green to brown with mottled, waxy or greasy luster; Mohs hardness about 2.5–4, white streak, poor cleavage, and fine-grained massive texture. The rounded, polished appearance indicates tumbling rather than natural crystal faces.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are hydrated during hydrothermal alteration, commonly along oceanic crust and tectonic plate boundaries. Serpentinization can occur from Precambrian to modern geological ages.
Uses & applications
Used as a decorative stone, carving material, tumbled-stone collectible, and occasionally architectural stone; fibrous chrysotile varieties historically supplied asbestos but should not be cut, drilled, or powdered.
Geological facts
Its green coloration comes from serpentine minerals and iron-bearing impurities; magnetite produced during alteration may make some specimens weakly magnetic.
Field identification & locations
Identify by mottled green-brown color, low hardness, waxy feel, and lack of visible granular crystals; common sources include California, Vermont, Italy, New Zealand, and the Canadian Appalachians. A small tumbled piece is typically worth $2–$10 USD.
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