mineral
Polished brecciated jasper
Jasper, microcrystalline quartz (SiO₂), with iron-oxide and silica vein infill
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; opaque reddish-brown with cream-white angular vein patterns, waxy to dull luster, and no visible cleavage. Its compact cryptocrystalline quartz structure gives it strong fracture resistance and typical specific gravity near 2.6.
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Physical properties
Hardness about 6.5–7 Mohs; opaque reddish-brown with cream-white angular vein patterns, waxy to dull luster, and no visible cleavage. Its compact cryptocrystalline quartz structure gives it strong fracture resistance and typical specific gravity near 2.6.
Formation & geological history
Forms when silica-rich fluids cement and replace volcanic or sedimentary material, with iron producing the red-brown color and later fractures filled by pale quartz or chalcedony. Deposits are generally Precambrian to younger, depending on locality.
Uses & applications
Commonly cut and polished as cabochons, palm stones, beads, carvings, and ornamental slabs; occasionally used for decorative stone. It has modest jewelry and collector value.
Geological facts
The contrasting pattern is brecciation: broken fragments were naturally recemented by mineral-rich fluids. Jasper is a variety of opaque chalcedony/microcrystalline quartz rather than a single strictly defined mineral species.
Field identification & locations
Identify it by its opaque reddish groundmass, creamy irregular veins, glassy-to-waxy polish, and inability to scratch with a steel knife if quartz-rich. Similar material occurs worldwide, notably India, Madagascar, Brazil, South Africa, and the western United States.
