igneous
Polished kambaba jasper (orbicular rhyolite)
Silicified orbicular rhyolite, commonly sold as kambaba jasper; orbicular patterns may include quartz, feldspar, and amphibole/chlorite minerals
AI-generated identification · may be incorrectDark green to black, polished, with rounded pale green-gray orbs; typically opaque with a waxy to vitreous luster. Hardness about 6–7 Mohs; fine-grained silica-rich matrix, with no visible cleavage. Exact mineralogy cannot be confirmed from the photo.
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Physical properties
Dark green to black, polished, with rounded pale green-gray orbs; typically opaque with a waxy to vitreous luster. Hardness about 6–7 Mohs; fine-grained silica-rich matrix, with no visible cleavage. Exact mineralogy cannot be confirmed from the photo.
Formation & geological history
A silica-rich volcanic rock whose rounded orbicular patterns formed during crystallization or later mineral alteration. Kambaba material is commonly marketed from Madagascar; its precise geological age and orbicule-forming process are not established by appearance alone.
Uses & applications
Used for polished spheres, beads, cabochons, and decorative objects; not generally an industrial stone.
Geological facts
“Kambaba jasper” is a trade name, not a formal mineral species, and the material is often identified geologically as orbicular rhyolite.
Field identification & locations
Look for the distinctive dark green matrix and rounded, contrasting orb-like markings. The photo shows a small polished sphere; provenance or testing would be needed for a definitive identification.
