metamorphic

Rounded gray-green metamorphic rock, likely serpentinite

Serpentinite; primarily serpentine-group minerals (lizardite/chrysotile/antigorite), commonly with magnetite and minor carbonate

AI-generated identification · may be incorrect

Fine-grained, rounded waterworn cobble with mottled gray-green color, dull to waxy luster, and pale veining. Typical hardness is about 2.5–4 Mohs; massive rather than visibly crystalline, with no obvious cleavage. Identification is provisional from the photograph.

Identified September 14, 2026More metamorphic →

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At a glance

Common name: Rounded gray-green metamorphic rock, likely serpentinite
Scientific name: Serpentinite; primarily serpentine-group minerals (lizardite/chrysotile/antigorite), commonly with magnetite and minor carbonate
Category: metamorphic
Identified: September 14, 2026
Method: Standard

AI Estimated Value

$1–$15 as a common cobble; approximately $20–$100+ if unusually patterned, polished, or confirmed high-quality carving stone.

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

Usually forms when ultramafic mantle rocks such as peridotite are hydrated during tectonic alteration, commonly in ophiolites and fault zones. The cobble’s smooth shape indicates stream or beach transport; the rock itself may be Mesozoic or younger depending on its source.

Uses & applications

Used as decorative stone, carving material, aggregate, and occasionally architectural stone. Chrysotile-bearing material has historical asbestos significance and should not be cut, drilled, or powdered without testing.

Geological facts

Serpentinite often has a slippery or waxy feel and may contain dark magnetite grains. The reported Baja California location is geologically plausible because serpentinite and other ophiolitic rocks occur in the region.

Field identification & locations

Check for a waxy feel, green streaks, unusually low hardness, and possible magnetism. A steel nail may scratch it; dilute acid usually produces little reaction unless carbonate veins are present. Similar-looking alternatives include altered basalt, greenstone, or chlorite-rich schist.