metamorphic

Weathered gray-green metamorphic rock, likely serpentinite or altered basalt

Serpentinite, chiefly serpentine-group minerals (antigorite/lizardite); identification is provisional from the photograph

AI-generated identification · may be incorrect

Fine-grained, rounded cobble with dull to weakly waxy luster, gray-green color, dark veins, and pits; typically Mohs 3–5, massive rather than visibly crystalline, with poor cleavage and specific gravity about 2.5–2.7.

Identified September 5, 2026More metamorphic →

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At a glance

Common name: Weathered gray-green metamorphic rock, likely serpentinite or altered basalt
Scientific name: Serpentinite, chiefly serpentine-group minerals (antigorite/lizardite); identification is provisional from the photograph
Category: metamorphic
Identified: September 5, 2026
Method: Standard

AI Estimated Value

Usually $2–$15 as a common cobble; $20–$100+ for polished, well-patterned, or locality-labeled specimens.

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

Likely formed by hydration and alteration of ultramafic mantle rock during tectonic activity, commonly in ophiolites and fault zones; age depends on locality and may range from Paleozoic to modern tectonic settings.

Uses & applications

Serpentinite is used as decorative stone, carving material, aggregate, and historically as a source of asbestos-bearing minerals; attractive polished pieces are collected, though fibrous material should not be cut or abraded.

Geological facts

The rounded shape indicates stream or shoreline transport and weathering. Green coloration, a waxy surface, and black veining support serpentinite, but a chemical test or locality information is needed to distinguish it from altered basalt or chlorite-rich metamorphic rock.

Field identification & locations

Common in tectonically active belts and ophiolite complexes, including California, Oregon, Italy, New Zealand, and parts of Canada. Check for a greasy/waxy feel, low hardness, and possible white-green streak; avoid inhaling dust.