metamorphic
Tumbled orbicular jasper (likely kambaba jasper)
Orbicular microcrystalline quartz–chalcedony aggregate; commonly sold as kambaba jasper
AI-generated identification · may be incorrectDark green to black rounded pebble with pale gray-green orbicular patches and a polished luster. Hardness is about 6.5–7 Mohs; opaque, fine-grained, with no visible cleavage and variable specific gravity around 2.6.
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Physical properties
Dark green to black rounded pebble with pale gray-green orbicular patches and a polished luster. Hardness is about 6.5–7 Mohs; opaque, fine-grained, with no visible cleavage and variable specific gravity around 2.6.
Formation & geological history
Formed from silica-rich volcanic or sedimentary material undergoing silicification and alteration, producing orbicular textures; its exact geological age depends on locality, commonly Precambrian to Paleozoic. The specimen is tumbled and polished.
Uses & applications
Used for cabochons, beads, carvings, lapidary pieces, and mineral collections; rarely used as a construction stone because it is generally sold in small pieces.
Geological facts
The distinctive circular markings are aggregates of chalcedony, quartz, and dark iron- or manganese-rich minerals rather than true crystals. “Kambaba jasper” is a commercial name and can refer to more than one visually similar material.
Field identification & locations
Identify by its opaque dark green-black body, rounded pale orbs, fine texture, and lack of metallic sparkle; common commercial sources include Madagascar and South Africa. A definitive identification may require locality information or microscopy.
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