metamorphic
Polished brecciated jasper
Jasper (microcrystalline quartz, SiO₂), likely brecciated and iron-oxide stained
AI-generated identification · may be incorrectOpaque, multicolored red, cream, gray, and brown; waxy to subvitreous luster; hardness about 6.5–7 Mohs; no visible cleavage; cryptocrystalline quartz with angular mineral fragments in a silica-rich matrix.
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Physical properties
Opaque, multicolored red, cream, gray, and brown; waxy to subvitreous luster; hardness about 6.5–7 Mohs; no visible cleavage; cryptocrystalline quartz with angular mineral fragments in a silica-rich matrix.
Formation & geological history
Forms when silica-rich groundwater cements and replaces fractured volcanic or sedimentary rock, with iron oxides producing red coloration. Most jasper is Phanerozoic or younger, though exact age depends on locality.
Uses & applications
Used for cabochons, beads, carvings, tumbled stones, and decorative objects; generally unsuitable for structural construction because specimens are small and ornamental.
Geological facts
The contrasting angular patches indicate brecciation rather than ordinary banding. Red colors commonly come from hematite or other iron oxides, while pale areas may contain quartz, chalcedony, or altered feldspar.
Field identification & locations
Identify it by its opaque appearance, high polish, hardness, and irregular red-and-cream breccia pattern; it will not fizz in dilute acid and typically scratches glass. Common sources include Oregon, Idaho, Nevada, Australia, South Africa, and Madagascar.
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