mineral
Polished orbicular jasper
Microcrystalline quartz (SiO₂) with iron-rich and altered volcanic inclusions
AI-generated identification · may be incorrectMohs hardness 6.5–7; gray-green to brown with rounded orbicular markings, waxy to vitreous luster, opaque, and no visible cleavage. The smooth shape is tumbled or polished, not natural crystal form.
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Physical properties
Mohs hardness 6.5–7; gray-green to brown with rounded orbicular markings, waxy to vitreous luster, opaque, and no visible cleavage. The smooth shape is tumbled or polished, not natural crystal form.
Formation & geological history
Jasper forms when silica-rich fluids replace or cement volcanic sediments and cavities; orbicular patterns develop from concentric mineral growth or altered inclusions. Specimen age depends on its source, commonly Paleozoic to Mesozoic volcanic terrains.
Uses & applications
Used for cabochons, beads, carvings, polished stones, and decorative objects; it has modest jewelry and collector appeal.
Geological facts
Jasper is a variety of chalcedony or microcrystalline quartz, and its patterns are caused by mineral impurities rather than quartz crystal faces.
Field identification & locations
Identify by its opaque body, fine grain, high polish, and distinctive rounded inclusions; test cautiously with a steel file, since quartz-rich jasper resists scratching. Similar material occurs in Madagascar, Mexico, Oregon, Indonesia, and Australia.
