metamorphic

Serpentine-rich metamorphic rock

Serpentinite, likely with magnetite and weathered ultramafic minerals

AI-generated identification · may be incorrect

Usually green to brown-black, mottled, waxy to dull luster, commonly massive with no visible crystal cleavage; hardness about 2.5–4, specific gravity roughly 2.5–2.7. The photograph suggests a weathered, iron-stained specimen, but exact identification requires testing.

Identified September 1, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when mantle-derived peridotite is hydrated and altered by hot, water-rich fluids, commonly along tectonic plate boundaries and ancient oceanic crust; ages vary widely from Paleozoic to recent. Green coloration comes mainly from serpentine-group minerals.

Uses & applications

Used as decorative stone, carvings, countertops, and historically as a source of asbestos-bearing material; attractive specimens are collected. Avoid cutting or abrading unknown serpentinite because some varieties contain fibrous asbestos minerals.

Geological facts

Serpentinite can contain magnetite, producing a weak magnetic response, and often develops a slippery or waxy surface. It is California’s state rock and occurs in many ophiolite belts.

Field identification & locations

Look for mottled apple-green to black color, low hardness, waxy texture, and possible magnetism; a streak, hardness, magnet, and thin-section/XRF test would improve identification. Common localities include California, Italy, New Zealand, Canada, and the Appalachians.