mineral
Tumbled yellow jasper or chert
Microcrystalline quartz (SiO₂), likely iron-stained jasper/chert
AI-generated identification · may be incorrectOpaque mustard-yellow, smooth tumbled surface, dull to waxy luster, no visible cleavage, cryptocrystalline structure; Mohs hardness about 6.5–7, specific gravity roughly 2.6. The rounded shape indicates mechanical polishing rather than natural weathering.
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Physical properties
Opaque mustard-yellow, smooth tumbled surface, dull to waxy luster, no visible cleavage, cryptocrystalline structure; Mohs hardness about 6.5–7, specific gravity roughly 2.6. The rounded shape indicates mechanical polishing rather than natural weathering.
Formation & geological history
Forms when silica-rich groundwater replaces or fills sediments, with iron oxides producing the yellow color; commonly Paleozoic to younger, though age depends on locality. Exact identification requires a hardness or specific-gravity test.
Uses & applications
Used for lapidary carvings, cabochons, beads, tumbled stones, and decorative objects; generally unsuitable as a major construction aggregate because of its small size and value as a polished specimen.
Geological facts
Jasper is an opaque variety of chalcedony, while chert is the broader silica-rich rock category; the boundary between yellow jasper and iron-stained chert can be indistinct.
Field identification & locations
Common in silica-rich sedimentary terrains worldwide, including the western United States, Mexico, Brazil, Australia, and Madagascar. It should scratch ordinary glass but not be scratched by a steel knife; a white streak and conchoidal fracture support quartz composition.
