metamorphic

Green-brown metamorphic rock, possibly serpentinite

Serpentinite, chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), with possible magnetite, chlorite, or carbonate

AI-generated identification · may be incorrect

Hardness typically 2.5–4 Mohs; mottled dark green, brown, and gray; waxy to greasy luster; commonly massive, fine-grained, and lacking visible crystal faces or strong cleavage. The specimen’s appearance is consistent with serpentinized ultramafic rock, though a photo cannot confirm the identification.

Identified September 22, 2026More metamorphic →

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At a glance

Common name: Green-brown metamorphic rock, possibly serpentinite
Scientific name: Serpentinite, chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), with possible magnetite, chlorite, or carbonate
Category: metamorphic
Identified: September 22, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a common rough specimen; $30–$150 if unusually attractive, polished, or locality-documented.

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 tectonic plate boundaries and ophiolites. Most examples formed during ancient oceanic or mountain-building events, with age varying by locality.

Uses & applications

Used as decorative stone, carvings, countertops, and occasionally construction aggregate; attractive material may be polished, but fibrous asbestos-bearing varieties require caution.

Geological facts

Often feels unusually smooth or greasy and may contain black magnetite veins or pale carbonate patches. Serpentinite is California’s state rock and commonly occurs with chromite and nickel deposits.

Field identification & locations

Look for green mottling, low hardness, waxy surfaces, and a white streak; avoid scratching unknown material containing possible asbestos fibers. Common in ophiolite belts worldwide, including California, Italy, New Zealand, and Canada.