metamorphic

Weathered greenstone (likely serpentinite or altered basalt)

Serpentinite, primarily Mg-rich serpentine minerals; possibly chlorite/actinolite-bearing altered mafic rock

AI-generated identification · may be incorrect

Dark olive-green, rounded and strongly weathered, with dull to waxy luster and no visible crystals or cleavage. Estimated Mohs hardness 3–6 depending on composition; relatively dense and fine-grained.

Identified September 8, 2026More metamorphic →

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At a glance

Common name: Weathered greenstone (likely serpentinite or altered basalt)
Scientific name: Serpentinite, primarily Mg-rich serpentine minerals; possibly chlorite/actinolite-bearing altered mafic rock
Category: metamorphic
Identified: September 8, 2026
Method: Standard

AI Estimated Value

Approximately $5–$30 as a common rounded specimen; $50–$200+ if verified as attractive serpentine, nephrite, or a documented locality piece.

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

Most likely formed by hydrothermal alteration of ultramafic mantle rock or mafic basalt, then rounded by river or shoreline transport; age cannot be determined from the photograph.

Uses & applications

Used as decorative stone, carvings, lapidary material, and occasionally architectural stone; usually modest collector value unless locality or pattern is exceptional.

Geological facts

The term “greenstone” is broad and can include serpentinite, altered basalt, chlorite schist, and nephrite-like rocks. Its smooth shape and muted green surface suggest natural water abrasion and weathering.

Field identification & locations

Common in ophiolite belts, former oceanic crust, and stream or beach gravels. A streak, hardness test, density, and examination of a fresh fracture are needed to distinguish serpentinite from greenstone or jade; avoid acid testing.