mineral
Polished brown jasper pebble
Jasper, an opaque microcrystalline variety of quartz (SiO₂), commonly colored by iron oxides
AI-generated identification · may be incorrectMohs hardness 6.5–7; brown to reddish-brown, opaque, with a glossy polish and cryptocrystalline quartz structure. It has no visible cleavage, conchoidal fracture, and specific gravity near 2.6.
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Physical properties
Mohs hardness 6.5–7; brown to reddish-brown, opaque, with a glossy polish and cryptocrystalline quartz structure. It has no visible cleavage, conchoidal fracture, and specific gravity near 2.6.
Formation & geological history
Forms when silica-rich groundwater fills cavities or replaces volcanic and sedimentary material, with iron producing the brown coloration; individual pieces may range from ancient Precambrian sources to younger river deposits. This specimen appears tumbled or smoothly polished.
Uses & applications
Used for beads, cabochons, carvings, ornamental objects, and lapidary collections; its durability makes it suitable for decorative stone but not typically fine jewelry gemstones.
Geological facts
Jasper is technically a rock composed mainly of microcrystalline quartz rather than a single mineral crystal. Brown varieties may be marketed as picture jasper, coffee jasper, or iron jasper depending on pattern and locality.
Field identification & locations
Identify it by its opaque earthy color, fine texture, glassy polish, and resistance to scratching by a steel knife; quartz-rich jasper should scratch glass. Common sources include India, Brazil, Madagascar, Australia, and the western United States.
