metamorphic
Polished orbicular jasper
Orbicular jasper; microcrystalline quartz (SiO₂) with iron oxides and altered volcanic minerals
AI-generated identification · may be incorrectTypically opaque gray, black, pink, and brown with rounded orbicular patterns; vitreous to waxy luster, cryptocrystalline structure, no cleavage, Mohs hardness about 6.5–7, and specific gravity near 2.6. The pictured piece appears polished or naturally smoothed.
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Physical properties
Typically opaque gray, black, pink, and brown with rounded orbicular patterns; vitreous to waxy luster, cryptocrystalline structure, no cleavage, Mohs hardness about 6.5–7, and specific gravity near 2.6. The pictured piece appears polished or naturally smoothed.
Formation & geological history
Forms when silica-rich fluids replace or cement volcanic rock, producing concentric mineral growths; commonly associated with altered Precambrian to Paleozoic volcanic terrains, depending on locality. Exact age and provenance require laboratory or locality data.
Uses & applications
Used for cabochons, carvings, beads, ornaments, and collector specimens; too variable and patterned for most architectural use.
Geological facts
Orbicular patterns may consist of concentric shells of feldspar, quartz, chlorite, hematite, or other alteration minerals rather than true fossils or “eyes.” Similar-looking orbicular rhyolite and ocean jasper can be difficult to separate visually.
Field identification & locations
Identify by its opaque silica-rich body, rounded concentric markings, hardness, and lack of visible glassy cleavage; it will generally scratch ordinary glass. Common sources include Madagascar, Australia, Mexico, and the western United States.
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