metamorphic

Serpentine-rich metamorphic rock

Serpentinite, likely antigorite/lizardite with magnetite and possible chlorite or talc

AI-generated identification · may be incorrect

Typically soft to moderately hard (Mohs 2.5–4), pale to dark green with black mottling, waxy to greasy luster, and massive rather than visibly crystalline texture. The dark grains may be magnetite, giving a magnetic response and a dark streak.

Identified September 7, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when ultramafic mantle rocks such as peridotite are hydrated and metamorphosed during tectonic activity, commonly along oceanic crust and subduction zones. Serpentinization occurs mainly at relatively low temperatures during geologically young-to-ancient tectonic alteration.

Uses & applications

Used as decorative and architectural stone, carvings, countertops, and historically as a source of asbestos-group minerals; fibrous varieties should not be cut or abraded because of health hazards. Attractive specimens are collected as ornamental rocks.

Geological facts

The specimen’s green-black, mottled appearance strongly suggests serpentinite, though image-only identification is not definitive. It may contain chrysotile or other serpentine minerals, so avoid generating dust.

Field identification & locations

Common in tectonic belts, ophiolites, and altered ultramafic terrains worldwide, including California, Italy, New Zealand, Canada, and the Appalachian region. Field tests include low hardness, waxy texture, green streak or powder, and possible magnetism; acid reaction is generally absent or weak.