metamorphic
Tumbled green-brown stone, likely serpentine
Serpentinite; chiefly serpentine-group minerals (antigorite, lizardite, chrysotile), commonly with magnetite
AI-generated identification · may be incorrectHardness about 2.5–4 Mohs; olive-green to brown, opaque, waxy to vitreous luster, fine-grained and massive with no visible crystal faces. The smooth shape indicates tumbling or polishing; exact identification requires testing.
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Physical properties
Hardness about 2.5–4 Mohs; olive-green to brown, opaque, waxy to vitreous luster, fine-grained and massive with no visible crystal faces. The smooth shape indicates tumbling or polishing; exact identification requires testing.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are hydrated during hydrothermal alteration, commonly in tectonic subduction zones. Serpentinization ranges from ancient Precambrian events to modern oceanic settings.
Uses & applications
Used as ornamental stone, carvings, beads, cabochons, and occasionally facing stone; historically used for tools and decorative objects. Chrysotile-rich material may contain hazardous asbestos fibers and should not be cut or powdered without controls.
Geological facts
Often resembles jade, but is generally softer and less durable. Magnetite inclusions can make some serpentinite weakly magnetic.
Field identification & locations
Common in ophiolite belts, California, Italy, New Zealand, and Canada; identify by olive color, waxy feel, low hardness, and sometimes a white streak. The image alone cannot exclude nephrite, chlorite, or another polished dark-green mineral.
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