metamorphic

Serpentinite (serpentinized ultramafic rock)

Serpentinite; chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), commonly with magnetite, brucite, and relict olivine/pyroxene

AI-generated identification · may be incorrect

Typically mottled olive-green, gray, black, and cream with waxy to greasy luster; hardness about 2.5–4 Mohs, massive texture, poor cleavage, and relatively high density (~2.5–2.7). The specimen’s pale veining and dark green patches are consistent with serpentinization, though a photo cannot exclude talc-rich ultramafic…

Identified August 20, 2026More metamorphic →

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At a glance

Common name: Serpentinite (serpentinized ultramafic rock)
Scientific name: Serpentinite; chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), commonly with magnetite, brucite, and relict olivine/pyroxene
Category: metamorphic
Identified: August 20, 2026
Method: Standard

AI Estimated Value

Typically $5–$40 as an ordinary field specimen; $50–$200+ for attractive polished or display-quality material.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Forms when mantle-derived peridotite is hydrated and altered by hydrothermal fluids, commonly along oceanic crust and plate-boundary fault zones. Most examples are Paleozoic to Mesozoic or younger, depending on the tectonic setting.

Uses & applications

Used as decorative and architectural stone, ornamental carvings, and historically as a source rock associated with asbestos minerals; cutting or sanding should be avoided until tested for fibrous asbestos.

Geological facts

Often contains magnetite, making some pieces weakly magnetic; polished surfaces can show striking green veining. Serpentinite is California’s state rock.

Field identification & locations

Identify by its green-black mottling, softness, waxy feel, curved fractures, and possible magnetism; common in ophiolite belts worldwide, including California, Italy, New Zealand, and the Appalachians.