metamorphic

Tumbled greenstone (likely serpentine or chlorite-rich stone)

Serpentinite, approximately Mg₃Si₂O₅(OH)₄; exact identification requires testing

AI-generated identification · may be incorrect

Small rounded, polished pebble with mottled gray-green color, waxy to dull luster, and no visible crystals or cleavage. Typical hardness is about 2.5–4 Mohs and specific gravity roughly 2.5–2.7; the dark pits may be natural inclusions or surface weathering.

Identified September 11, 2026More metamorphic →

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At a glance

Common name: Tumbled greenstone (likely serpentine or chlorite-rich stone)
Scientific name: Serpentinite, approximately Mg₃Si₂O₅(OH)₄; exact identification requires testing
Category: metamorphic
Identified: September 11, 2026
Method: Standard

AI Estimated Value

About $1–$10 for a common tumbled pebble; $10–$30 if unusually attractive, larger, or from a documented locality.

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 hydrothermal alteration of ultramafic mantle rock, commonly during tectonic plate interaction; serpentinite can range from Precambrian to modern geologic settings. The specimen has been naturally or mechanically tumbled and polished.

Uses & applications

Used as an ornamental stone, carving material, tumbled stone, and occasionally as a low-grade gemstone; massive serpentinite is also used decoratively in architecture, though asbestos-bearing varieties require care.

Geological facts

Greenstone is a trade term covering several rocks, including serpentine, chlorite schist, and altered basalt, so visual identification is uncertain from one photograph.

Field identification & locations

Common in ophiolite belts and subduction-related terrains, including California, Italy, New Zealand, and Canada. A waxy feel, low hardness, pale green streak, and resistance to dilute acid support serpentine; avoid grinding unknown serpentinite because some varieties contain asbestos minerals.