mineral
Tumbled yellow chalcedony (likely silicified material)
Microcrystalline quartz, SiO₂; possibly iron-stained chalcedony or fossilized/silicified limestone
AI-generated identification · may be incorrectHardness about 6.5–7, pale honey-yellow, waxy to dull luster, cryptocrystalline quartz with no visible cleavage; rounded and polished/tumbled. The small pits and mottling may reflect weathering, inclusions, or dissolved fossil grains.
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Physical properties
Hardness about 6.5–7, pale honey-yellow, waxy to dull luster, cryptocrystalline quartz with no visible cleavage; rounded and polished/tumbled. The small pits and mottling may reflect weathering, inclusions, or dissolved fossil grains.
Formation & geological history
Chalcedony forms when silica-rich groundwater fills cavities and fractures, commonly in volcanic rocks or sedimentary deposits; yellow color usually comes from iron oxides. Exact geological age and identity cannot be determined from the photograph alone.
Uses & applications
Used as a lapidary stone, cabochon, bead, or decorative specimen; ordinary pieces have modest value.
Geological facts
A glassy scratch test is useful: chalcedony should scratch ordinary glass, though surface polish can complicate testing. Acid fizzing would suggest calcite rather than quartz, while a steel point should not scratch chalcedony.
Field identification & locations
Commonly found in silica-rich gravels, volcanic cavities, and sedimentary beds worldwide; examine translucency, conchoidal fracture, hardness, and absence of cleavage. The specimen appears human-tumbled.
