mineral
Tumbled pale-green stone, likely prehnite or serpentine
Most consistent with massive prehnite, Ca₂Al₂Si₃O₁₀(OH)₂; serpentine is a possible alternative
AI-generated identification · may be incorrectPale blue-green, opaque to translucent, waxy-to-dull luster, rounded and polished; hardness approximately Mohs 6–6.5 for prehnite (serpentine 2.5–5.5), with no obvious cleavage. Exact identification requires hardness, streak, and possibly chemical or microscopic testing.
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Physical properties
Pale blue-green, opaque to translucent, waxy-to-dull luster, rounded and polished; hardness approximately Mohs 6–6.5 for prehnite (serpentine 2.5–5.5), with no obvious cleavage. Exact identification requires hardness, streak, and possibly chemical or microscopic testing.
Formation & geological history
Prehnite commonly forms as a secondary mineral in cavities and fractures of basalt and other volcanic rocks, generally in relatively young hydrothermal systems; serpentine forms by alteration of ultramafic rocks. The image alone cannot establish geological age.
Uses & applications
Used as a lapidary stone, carving material, and inexpensive cabochon or tumbled stone; massive material has little industrial use.
Geological facts
The rounded shape and uniform surface indicate human tumbling or water wear rather than a crystal specimen. Prehnite may show botryoidal forms and subtle pearly translucence, while serpentine is typically softer and more waxy.
Field identification & locations
Look for pale green color, translucence at thin edges, and hardness sufficient to scratch glass for prehnite; a steel nail may scratch serpentine but usually not prehnite. Common sources include Australia, South Africa, India, China, and the United States.
