metamorphic

Serpentinite (likely)

Serpentinite; chiefly serpentine-group minerals (antigorite, lizardite, chrysotile), commonly after peridotite

AI-generated identification · may be incorrect

Dark gray-green, mottled, fine-grained, waxy to subvitreous luster with smooth rounded surfaces; Mohs hardness about 2.5–4, typically massive with no visible crystal structure. The specimen may contain black magnetite and relict pyroxene.

Identified September 17, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when ultramafic mantle rocks hydrate during low-temperature metamorphism, commonly along faults and subduction zones; ages vary from Precambrian to modern tectonic settings.

Uses & applications

Used as decorative stone, carvings, countertops, and historically as a source of asbestos-bearing material; ordinary rounded pieces have little commercial value.

Geological facts

Serpentinite commonly preserves veining and mesh textures produced as olivine alters to serpentine. Some varieties can resemble jade but are generally softer and less durable.

Field identification & locations

Common in ophiolites and tectonic belts, including California, the Appalachians, New Zealand, and Italy; identify by green color, waxy feel, low hardness, and possible magnetism. The photo alone cannot exclude altered basalt or another dark-green metamorphic rock.