metamorphic

Weathered greenstone (likely serpentinite or altered basalt)

Serpentinite-group rock, commonly dominated by serpentine minerals (antigorite/lizardite); exact identification requires testing

AI-generated identification · may be incorrect

Pale olive-green, mottled, dull to waxy luster, fine-grained and brecciated-looking; typically Mohs 2.5–4, with no obvious cleavage. The rounded shape and surface cracking indicate strong weathering or stream abrasion.

Identified August 8, 2026More metamorphic →

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At a glance

Common name: Weathered greenstone (likely serpentinite or altered basalt)
Scientific name: Serpentinite-group rock, commonly dominated by serpentine minerals (antigorite/lizardite); exact identification requires testing
Category: metamorphic
Identified: August 8, 2026
Method: Standard

AI Estimated Value

About $2–$15 for a common weathered specimen; $20–$75 if unusually attractive, polished, or scientifically documented.

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 when ultramafic mantle rock was hydrothermally altered to serpentine, or when basalt underwent low-grade metamorphism; age depends on its source terrane. Common in ophiolites and tectonic suture zones.

Uses & applications

Serpentinite is used as decorative stone, aggregate, and occasionally carving material; specimens have modest collector interest. Avoid dust, since some serpentinite deposits may contain asbestos-forming minerals.

Geological facts

Greenstone is a field term and can include several rocks, so this identification is provisional. A white streak, low hardness, and possible magnetism would help distinguish serpentinite from altered basalt or chlorite-rich rock.

Field identification & locations

Common in California, Italy, New Zealand, Oman, the Appalachians, and other ophiolite belts. Test hardness against a fingernail or copper coin, inspect a fresh surface, and use a magnet; laboratory thin-section or XRD testing is definitive.