mineral
Tumbled chalcedony / quartz pebble
Microcrystalline quartz (SiO₂), likely chalcedony with iron-oxide staining
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; cream to honey-yellow, translucent edges, waxy to dull luster, cryptocrystalline structure, and no obvious cleavage. The rounded surface and conchoidal fracture suggest natural abrasion of quartz-rich material.
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Physical properties
Hardness 6.5–7 Mohs; cream to honey-yellow, translucent edges, waxy to dull luster, cryptocrystalline structure, and no obvious cleavage. The rounded surface and conchoidal fracture suggest natural abrasion of quartz-rich material.
Formation & geological history
Formed when silica-rich groundwater precipitated microscopic quartz fibers in cavities or fractures, probably during later alteration of volcanic or sedimentary rock; its precise geological age cannot be determined from the image. Stream or shoreline transport likely produced the rounded shape.
Uses & applications
Used as a lapidary stone, cabochon, tumbled stone, or collector specimen; quality depends on translucency, color, pattern, and polish. It has little industrial value as an isolated pebble.
Geological facts
The yellow-brown color commonly comes from hydrated iron oxides or included clay minerals rather than the quartz itself. Chalcedony can grade visually into jasper when opaque and strongly colored.
Field identification & locations
Identify by its glassy-to-waxy appearance, very high hardness, lack of cleavage, and conchoidal fracture; it should scratch ordinary glass but not be scratched by a steel knife. Common in volcanic cavities, river gravels, and silica-rich sedimentary environments worldwide.
