metamorphic

Tumbled green-brown stone, likely serpentine

Serpentinite; chiefly serpentine-group minerals (antigorite, lizardite, chrysotile), commonly with magnetite

AI-generated identification · may be incorrect

Mohs hardness about 2.5–5.5; olive-green to brown, waxy or greasy luster, fine-grained and massive, with no obvious cleavage. The rounded, glossy surface indicates tumbling or polishing; exact identification is uncertain from the photo alone.

Identified September 21, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when ultramafic mantle rocks such as peridotite are hydrated and altered during metamorphism, commonly in oceanic crust and subduction zones. These rocks range from Precambrian to geologically recent.

Uses & applications

Used as ornamental stone, carvings, cabochons, and polished specimens; some serpentinite has been used in architecture. Avoid cutting or sanding unknown material because chrysotile-bearing varieties may contain asbestos fibers.

Geological facts

Serpentinite is California’s state rock and commonly displays mottled green, brown, and black patterns. Its relatively low hardness allows scratching by a steel knife in softer varieties.

Field identification & locations

Common in California, Oregon, Washington, New Zealand, Italy, Greece, and many ophiolite belts. Confirm with streak, hardness, density, and mineralogical testing; the image could also represent another dark, polished stone such as basalt or jasper.