metamorphic

Greenstone pebble, likely serpentine or altered basalt

Probably serpentinite (serpentine-group minerals, Mg₃Si₂O₅(OH)₄) or chlorite-rich greenschist

AI-generated identification · may be incorrect

Smooth, water-worn oval with mottled dark olive-green color and dull to slightly waxy luster; likely Mohs 2.5–4.5, with no visible crystals or cleavage. Exact identification requires hardness, streak, density, and possibly microscopy or X-ray analysis.

Identified September 14, 2026More metamorphic →

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At a glance

Common name: Greenstone pebble, likely serpentine or altered basalt
Scientific name: Probably serpentinite (serpentine-group minerals, Mg₃Si₂O₅(OH)₄) or chlorite-rich greenschist
Category: metamorphic
Identified: September 14, 2026
Method: Standard

AI Estimated Value

About $1–$10 as a common tumbled or beach pebble; $10–$50 if confirmed, attractive, and polished.

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 low- to moderate-temperature hydrothermal alteration of ultramafic rock, or metamorphism of basalt; ages vary widely from Precambrian to recent geologic settings. Its rounded shape indicates transport and abrasion in a stream, beach, or glacial environment.

Uses & applications

Commonly collected as a polished or tumbled stone and sometimes carved; serpentine is used decoratively and occasionally as a low-cost ornamental stone. It has little value as an unverified pebble.

Geological facts

Serpentine can resemble jade, but it is generally softer and less dense; some varieties may contain asbestos-form minerals, so avoid cutting or generating dust until identified.

Field identification & locations

Look for a greasy or waxy feel, green-black mottling, and softness relative to quartz; a steel knife may scratch many serpentinites, while quartz will not. Common sources include California, Oregon, Italy, New Zealand, and serpentinite belts worldwide.