mineral
Polished orbicular jasper (likely kambaba jasper)
Orbicular microcrystalline quartz–feldspar aggregate; commonly sold as Kambaba jasper
AI-generated identification · may be incorrectDark green-black polished surface with pale gray-green orbicular markings and a vitreous to waxy luster; opaque, cryptocrystalline, typically Mohs 6.5–7, with no visible cleavage and specific gravity around 2.6–2.8.
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Physical properties
Dark green-black polished surface with pale gray-green orbicular markings and a vitreous to waxy luster; opaque, cryptocrystalline, typically Mohs 6.5–7, with no visible cleavage and specific gravity around 2.6–2.8.
Formation & geological history
Forms from silica-rich volcanic or sedimentary material that recrystallized into patterned jasper; commercial Kambaba jasper is chiefly associated with Madagascar, though similar orbicular jaspers occur worldwide. Exact geological age depends on locality.
Uses & applications
Used for cabochons, beads, carvings, polished palm stones, and decorative objects; valued mainly as an ornamental lapidary material rather than a gemstone of high rarity.
Geological facts
The circular markings are orbicules produced by contrasting mineral aggregates, often involving quartz, feldspar, chlorite, and amphibole-group minerals. Trade names may be applied inconsistently to visually similar orbicular jaspers.
Field identification & locations
Identify it by its very dark green-black base, pale rounded patterns, opaque body, and ability to take a smooth polish; it should not show glassy transparency or strong cleavage. Common sources include Madagascar, Mexico, Australia, and the United States.
