metamorphic

Dark green-black metamorphic rock, likely serpentinite

Serpentinite; chiefly serpentine-group minerals, commonly antigorite, lizardite, or chrysotile, with magnetite and minor chromite

AI-generated identification · may be incorrect

Typically green to black, waxy to greasy luster, fine-grained and massive; Mohs hardness about 2.5–4, with poor or absent cleavage and specific gravity roughly 2.5–2.7. The specimen’s rounded, sparkling surface may reflect polished or weathered serpentinite, though exact identification requires testing.

Identified September 17, 2026More metamorphic →

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At a glance

Common name: Dark green-black metamorphic rock, likely serpentinite
Scientific name: Serpentinite; chiefly serpentine-group minerals, commonly antigorite, lizardite, or chrysotile, with magnetite and minor chromite
Category: metamorphic
Identified: September 17, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a common hand specimen; $30–$150 for attractive polished or strongly patterned 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 ultramafic mantle rocks such as peridotite undergo low-temperature hydration during tectonic subduction or seafloor alteration. Serpentinization is commonly Paleozoic to Cenozoic in exposed ophiolite belts, but the specimen’s age cannot be determined visually.

Uses & applications

Used as decorative stone, carvings, tiles, countertops, and occasionally ornamental gemstone material; historically used for architectural facing. Chrysotile-bearing varieties may contain asbestos and should not be cut or powdered without testing.

Geological facts

Often contains magnetite, making some pieces weakly magnetic; it may show slick, rounded surfaces and dark green veining. Similar-looking rocks include chlorite schist, basalt, and polished greenstone.

Field identification & locations

Common in ophiolites and tectonic fault zones, including California, Italy, New Zealand, Canada, and the Appalachians. A streak, hardness, magnetism, and thin-section or Raman/XRD analysis can confirm it.