metamorphic

Serpentinite (serpentinized ultramafic rock), possibly with chromite

Serpentine-group minerals, chiefly lizardite and chrysotile; commonly derived from peridotite or pyroxenite, with possible chromite and magnetite

AI-generated identification · may be incorrect

Typically green to black, mottled, waxy to greasy luster; Mohs hardness 2.5–5.5, nonfoliated to weakly schistose, with poor cleavage. The specimen shows green-yellow alteration, dark opaque grains, and rusty iron-oxide staining.

Identified September 12, 2026More metamorphic →

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At a glance

Common name: Serpentinite (serpentinized ultramafic rock), possibly with chromite
Scientific name: Serpentine-group minerals, chiefly lizardite and chrysotile; commonly derived from peridotite or pyroxenite, with possible chromite and magnetite
Category: metamorphic
Identified: September 12, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a common hand specimen; $40–$150 for attractive polished or mineral-rich pieces.

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 hydrates during low-temperature metamorphism, commonly along oceanic crust, faults, and subduction zones; ages vary widely from Precambrian to recent tectonic exposure.

Uses & applications

Used as decorative stone, carving material, aggregate, and historically as a source of asbestos-bearing serpentine; attractive pieces are collected, though fibrous material should not be cut or powdered.

Geological facts

Serpentinite often contains magnetite and may be weakly magnetic; associated chromite can produce black, granular patches. It is the characteristic rock of many ophiolite belts.

Field identification & locations

Identify by its green-black mottled color, waxy surface, low hardness, and association with dark ultramafic cobbles; a streak, magnet, and acid test can help, but avoid disturbing possible asbestos fibers. Common in California, the Appalachians, New Zealand, and ophiolite zones worldwide.