metamorphic
Orbicular jasper (likely kambaba jasper)
Silicified microcrystalline quartz and chalcedony with dark-green amphibole or other mafic mineral inclusions; trade name “kambaba jasper”
AI-generated identification · may be incorrectPolished, opaque pale gray-green sphere with dark green-black orbicular patterns; Mohs hardness about 6.5–7, waxy to vitreous luster, microcrystalline structure, and no visible cleavage. The image alone cannot confirm the exact material; similar orbicular stones are sold under several jasper trade names.
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Physical properties
Polished, opaque pale gray-green sphere with dark green-black orbicular patterns; Mohs hardness about 6.5–7, waxy to vitreous luster, microcrystalline structure, and no visible cleavage. The image alone cannot confirm the exact material; similar orbicular stones are sold under several jasper trade names.
Formation & geological history
Silica-rich material formed as volcanic or sedimentary rock was silicified, with contrasting rounded mineral aggregates producing the orbicular pattern; specimens sold as kambaba jasper are commonly attributed to Madagascar and South Africa, though trade identification can be unreliable.
Uses & applications
Used for beads, cabochons, spheres, and ornamental carvings; valued mainly as a decorative lapidary stone.
Geological facts
“Kambaba jasper” is a commercial name and is not necessarily true jasper; the distinctive dark rounded markings are its key visual feature.
Field identification & locations
Check for a dense, opaque stone with naturally irregular dark orbicular markings and a hard, glassy-to-waxy polish; verify identity with mineralogical testing if provenance matters.
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