mineral
Tumbled yellow jasper or chert
Microcrystalline quartz (SiO₂), likely iron-stained jasper/chert
AI-generated identification · may be incorrectOpaque mustard-yellow to tan, smoothly rounded and polished, with a dull-to-waxy luster; quartz hardness is about 7 Mohs, no visible cleavage, and typical specific gravity is 2.55–2.70. The fine-grained texture suggests cryptocrystalline quartz rather than a visibly crystalline mineral.
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Physical properties
Opaque mustard-yellow to tan, smoothly rounded and polished, with a dull-to-waxy luster; quartz hardness is about 7 Mohs, no visible cleavage, and typical specific gravity is 2.55–2.70. The fine-grained texture suggests cryptocrystalline quartz rather than a visibly crystalline mineral.
Formation & geological history
Forms when silica-rich fluids replace or cement sediments, commonly with iron oxides producing the yellow-brown color; its exact geological age cannot be determined from the photograph. The specimen appears human-tumbled and polished.
Uses & applications
Used as a lapidary stone for cabochons, beads, carvings, and decorative objects; common tumbled pieces generally have modest value.
Geological facts
Jasper is an opaque variety of chalcedony or microcrystalline quartz, while chert is a closely related silica-rich rock. Yellow coloration commonly reflects goethite or limonite inclusions.
Field identification & locations
Identify by its opaque, fine-grained appearance, glass-scratching hardness, and lack of cleavage; acid does not typically fizz. Exact identification requires tests such as streak, hardness, specific gravity, or microscopy.
