mineral
Polished brown jasper (likely picture jasper)
Microcrystalline quartz/chalcedony, SiO₂, with iron-oxide and clay inclusions
AI-generated identification · may be incorrectTypically Mohs hardness 6.5–7, opaque brown to tan with flowing bands, earthy colors, waxy to glassy luster, and no visible cleavage; massive, fine-grained cryptocrystalline structure. The rounded, glossy surface indicates tumbling or polishing.
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Physical properties
Typically Mohs hardness 6.5–7, opaque brown to tan with flowing bands, earthy colors, waxy to glassy luster, and no visible cleavage; massive, fine-grained cryptocrystalline structure. The rounded, glossy surface indicates tumbling or polishing.
Formation & geological history
Forms when silica-rich groundwater fills or replaces volcanic sediments and fractures, with iron and clay producing the brown patterning. Individual material may range from Paleozoic to Cenozoic in age, depending on locality.
Uses & applications
Used for cabochons, carvings, beads, bookends, and ornamental objects; attractive patterned pieces are popular with collectors. It has little industrial value compared with ordinary quartz.
Geological facts
Jasper is an opaque variety of chalcedony and is technically a rock-like aggregate rather than a single crystal. “Picture jasper” is a trade term for strongly scenic or banded patterns.
Field identification & locations
Identify by its opaque brown coloration, very fine texture, hardness, and inability to scratch with a steel knife; it should scratch glass but not be scratched by steel. Common sources include Oregon, Idaho, Utah, Arizona, Mexico, Madagascar, and Australia.
