mineral
Polished/tumbled chalcedony (likely agate or jasper)
Microcrystalline quartz, SiO₂; possibly quartz-rich silicified material
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; cream, honey-yellow, white, and brown coloration with waxy to dull luster and no obvious cleavage. The irregular, partly polished surface and granular patches suggest chalcedony mixed with opaque jasper or weathered matrix.
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Physical properties
Hardness about 6.5–7 Mohs; cream, honey-yellow, white, and brown coloration with waxy to dull luster and no obvious cleavage. The irregular, partly polished surface and granular patches suggest chalcedony mixed with opaque jasper or weathered matrix.
Formation & geological history
Forms when silica-rich groundwater fills cavities, fractures, or porous volcanic rock, later hardening into chalcedony and agate/jasper. Precise geological age and locality cannot be determined from the photograph.
Uses & applications
Used for ornamental stones, cabochons, carvings, beads, and lapidary specimens; lower-grade pieces have modest collecting value.
Geological facts
Agate is banded chalcedony, whereas jasper is opaque and commonly contains iron oxides or other impurities; this specimen appears more jasper-like than a clean agate.
Field identification & locations
Field identification: glassy or waxy appearance, conchoidal fracture, lack of cleavage, and inability to scratch it with a steel knife; quartz should scratch ordinary glass. Common worldwide, especially volcanic regions and river gravels.
