metamorphic
Polished orbicular jasper (likely kambaba or ocean jasper)
Silicified microcrystalline quartz/chalcedony with iron-rich inclusions; mainly SiO₂
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; black, gray, and cream orbicular pattern with a waxy-to-glassy polish. Cryptocrystalline quartz has no visible cleavage and typically has specific gravity near 2.6.
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Physical properties
Hardness about 6.5–7 Mohs; black, gray, and cream orbicular pattern with a waxy-to-glassy polish. Cryptocrystalline quartz has no visible cleavage and typically has specific gravity near 2.6.
Formation & geological history
Formed by silica-rich fluids replacing or cementing volcanic material, while iron- and manganese-rich minerals produced the contrasting orbs; such deposits are commonly Precambrian to Paleozoic in age. The specimen is tumbled and polished.
Uses & applications
Used for cabochons, beads, carvings, palm stones, and decorative objects; value is primarily aesthetic and collectible rather than industrial.
Geological facts
Orbicular jasper is often marketed as ocean jasper or kambaba jasper, though these trade names can overlap and are not always mineralogically precise.
Field identification & locations
Identify it by its opaque body, rounded concentric orbs, quartz-like hardness, and absence of cleavage; common sources include Madagascar, South Africa, and Mexico. A definitive locality requires provenance or laboratory testing.
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