metamorphic

Tumbled greenstone (likely serpentine)

Serpentinite; chiefly serpentine-group minerals, Mg₃Si₂O₅(OH)₄

AI-generated identification · may be incorrect

Hardness about 2.5–4 Mohs; dark olive to yellow-green, waxy to greasy luster, opaque, and commonly massive rather than visibly crystalline. The smooth surface is tumbled/polished, and the specimen may contain darker magnetite or other alteration minerals.

Identified September 15, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when ultramafic mantle rocks such as peridotite undergo hydration and metamorphic alteration, commonly along ancient oceanic crust and subduction zones. Serpentinite ranges from Precambrian to modern geological ages.

Uses & applications

Used as a decorative stone, carvings, beads, and low-grade ornamental “greenstone”; some varieties are used as dimension stone. It is generally unsuitable for jewelry requiring high scratch resistance.

Geological facts

The appearance can overlap with nephrite jade, but serpentine is softer and usually less tough. Avoid generating dust from cutting or sanding, because some serpentinites may contain asbestos-form minerals.

Field identification & locations

Common in California, the Appalachians, New Zealand, Italy, Canada, and ultramafic terrains worldwide. Field clues include olive-green color, waxy feel, low hardness, and occasional black veining; definitive identification requires testing or analysis.