mineral
Tumbled green-yellow chalcedony (likely prehnite or serpentine)
Cryptocrystalline quartz (chalcedony), SiO₂; identification is uncertain from the photograph
AI-generated identification · may be incorrectTranslucent olive-green to yellow, smooth tumbled surface, vitreous-to-waxy luster, and no visible crystal faces or cleavage. Likely hardness about 6–7 Mohs if chalcedony; the rounded shape is human-processed.
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Physical properties
Translucent olive-green to yellow, smooth tumbled surface, vitreous-to-waxy luster, and no visible crystal faces or cleavage. Likely hardness about 6–7 Mohs if chalcedony; the rounded shape is human-processed.
Formation & geological history
Chalcedony forms when silica-rich groundwater fills cavities and fractures, commonly in volcanic rocks; deposits range from ancient to geologically recent. Similar green material may instead be prehnite or serpentine, requiring hardness and refractive tests.
Uses & applications
Used as a decorative tumbled stone, cabochon, carving material, and inexpensive jewelry stone; chalcedony is also used for ornamental objects.
Geological facts
Green chalcedony is often marketed as chrysoprase when its color is strong and nickel-related. The image alone cannot reliably distinguish it from dyed agate, prehnite, or serpentine.
Field identification & locations
Test an inconspicuous area: chalcedony scratches glass and does not scratch easily with steel; serpentine is much softer. Common sources include Brazil, India, Madagascar, Australia, and the United States.
