metamorphic

Tumbled greenstone, likely serpentine or altered basalt

Probable serpentinite (Mg-rich phyllosilicates, chiefly antigorite/lizardite) or chlorite-rich basalt

AI-generated identification · may be incorrect

Dark green-gray, rounded and polished, with fine-grained texture and subdued waxy to dull luster. Likely Mohs 3–6 depending on composition; no visible cleavage or crystals, and specific gravity commonly about 2.6–3.0.

Identified September 1, 2026More metamorphic →

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At a glance

Common name: Tumbled greenstone, likely serpentine or altered basalt
Scientific name: Probable serpentinite (Mg-rich phyllosilicates, chiefly antigorite/lizardite) or chlorite-rich basalt
Category: metamorphic
Identified: September 1, 2026
Method: Standard

AI Estimated Value

About $1–$10 for a common tumbled piece; unusual color, provenance, or polished larger specimens may reach $20–$50.

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

If serpentinite, it formed when oceanic ultramafic rock hydrated during metamorphism, commonly in ophiolite belts; if basaltic greenstone, it reflects low-grade metamorphism. Exact age and identity cannot be determined from the photograph.

Uses & applications

Used as a decorative tumbled stone, ornamental carving material, and occasionally in landscaping; typically not a gemstone of high commercial value.

Geological facts

The term “greenstone” is a trade and field name rather than a single mineral. Serpentine may feel slightly soapy and can scratch relatively easily, while basaltic greenstone is harder and denser.

Field identification & locations

Common in metamorphic terrains and glacial gravels. Test with a steel knife or glass cautiously: easy scratching suggests serpentine; stronger resistance suggests basalt/greenstone. A streak, hardness, and specific-gravity test would improve identification.