metamorphic

Serpentinite (likely serpentinized ultramafic rock)

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

AI-generated identification · may be incorrect

Hardness typically 2.5–4 Mohs; mottled yellow-green to dark green, waxy to greasy luster, fine-grained and massive, with no obvious cleavage. The specimen’s granular yellow-green appearance is consistent with serpentinization, though a photo cannot exclude greenstone or weathered peridotite.

Identified September 12, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when mantle peridotite reacts with water during ocean-floor alteration or tectonic metamorphism; commonly Paleozoic to Mesozoic in exposed ophiolite belts, but age varies widely.

Uses & applications

Used as ornamental stone, carving material, aggregate, and historically as a decorative building stone; collectible value is generally modest unless attractively patterned or associated with asbestos minerals.

Geological facts

Serpentinite often contains magnetite and may be weakly magnetic. Some varieties can host chrysotile asbestos, so avoid cutting, grinding, or generating dust without proper testing and protection.

Field identification & locations

Look for a green-yellow mottled color, smooth/waxy surface, low hardness, and occasional magnetism; common in California, Italy, New Zealand, the Alps, and ophiolite complexes worldwide. Estimated value: $5–$30 for a small rough specimen; $30–$150 if polished or unusually attractive.