mineral
Polished orbicular jasper
Jasper, microcrystalline quartz (SiO₂), with iron oxides and other inclusions
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; opaque, cream to brown and black orbicular patterns; vitreous to waxy luster and no visible cleavage. The rounded shape and smooth surface indicate tumbling or polishing.
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Physical properties
Hardness about 6.5–7 Mohs; opaque, cream to brown and black orbicular patterns; vitreous to waxy luster and no visible cleavage. The rounded shape and smooth surface indicate tumbling or polishing.
Formation & geological history
Jasper forms when silica-rich fluids replace or cement volcanic ash, sediment, or existing rock, with iron and manganese producing the dark patterns; its exact geological age and locality cannot be determined from the image. Orbicular varieties commonly form in volcanic environments.
Uses & applications
Used for cabochons, beads, carvings, polished display stones, and inexpensive jewelry; occasionally used as decorative architectural stone.
Geological facts
Orbicular jasper patterns are made by concentric or radiating mineral growth and alteration, not fossils. The appearance can overlap with ocean jasper, leopard jasper, or other patterned jaspers.
Field identification & locations
Identify it by its opaque composition, glassy/waxy polish, hardness, and irregular orb-like inclusions; it will not usually fizz in dilute acid. Common sources include Madagascar, Mexico, Oregon, and Australia, though locality requires provenance or testing.
