mineral

Tumbled green-gray stone, likely prehnite or serpentine

Likely prehnite, Ca₂Al₂Si₃O₁₀(OH)₂; identification is uncertain from the photograph

AI-generated identification · may be incorrect

Pale green-gray, opaque to translucent, with a dull-to-waxy luster and rounded tumbled form; likely Mohs 6–6.5 if prehnite, or 2.5–4 if serpentine. No visible crystal faces or cleavage are apparent.

Identified August 16, 2026More mineral →

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At a glance

Common name: Tumbled green-gray stone, likely prehnite or serpentine
Scientific name: Likely prehnite, Ca₂Al₂Si₃O₁₀(OH)₂; identification is uncertain from the photograph
Category: mineral
Identified: August 16, 2026
Method: Standard

AI Estimated Value

Approximately $2–$15 for a common tumbled piece; attractive translucent or unusual specimens may sell for $20–$75.

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

Prehnite forms in low-temperature hydrothermal veins and cavities of basaltic rocks, commonly during alteration of volcanic rocks; many deposits are Mesozoic to younger. Serpentine instead forms by hydration of ultramafic mantle rocks.

Uses & applications

Used as a lapidary stone, cabochon, bead, and collector specimen; not generally used for construction in this small polished form.

Geological facts

Prehnite commonly shows pale green color and botryoidal or fibrous interiors, sometimes with darker inclusions. A hardness or specific-gravity test is needed to distinguish it from serpentine, jade, or dyed quartz.

Field identification & locations

Common sources include Australia, South Africa, China, India, and the United States. Check streak, hardness, translucency, and heft; avoid relying on color alone because the image is insufficient for confident identification.