metamorphic
Orbicular jasper
Silica-rich microcrystalline quartz/chalcedony (SiO₂), commonly with iron oxides and other silicates
AI-generated identification · may be incorrectTypically opaque, mottled red-brown, cream, and gray-green with orbicular or brecciated patterns; Mohs hardness 6.5–7, vitreous to dull/waxy luster, cryptocrystalline structure, no cleavage, and specific gravity about 2.5–2.7.
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Physical properties
Typically opaque, mottled red-brown, cream, and gray-green with orbicular or brecciated patterns; Mohs hardness 6.5–7, vitreous to dull/waxy luster, cryptocrystalline structure, no cleavage, and specific gravity about 2.5–2.7.
Formation & geological history
Forms when silica-rich volcanic material is altered and recrystallized, producing jasper or orbicular textures; exact age depends on locality, commonly Paleozoic to Cenozoic. The image may also represent brecciated jasper rather than true orbicular jasper.
Uses & applications
Used for cabochons, beads, carvings, polished specimens, and ornamental objects; it has little industrial value compared with ordinary aggregate.
Geological facts
Its striking patterns result from chalcedony or quartz surrounding contrasting mineral-rich fragments or spherules, often colored by hematite, goethite, chlorite, or epidote.
Field identification & locations
Identify it by its opaque hardness, waxy-to-glassy fracture, and inability to scratch with a steel knife easily; common sources include Madagascar, Oregon, Mexico, India, and Australia. A locality label is important because appearance overlaps with rhyolite and brecciated agate.
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