metamorphic
Polished orbicular jasper (likely ocean jasper)
Silicified volcanic rock; microcrystalline quartz/chalcedony (SiO₂) with iron oxides and altered volcanic minerals
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; opaque, olive-green, brown, mustard-yellow, cream, and white orbicular pattern; waxy to glossy luster after polishing; cryptocrystalline quartz with no visible cleavage and uneven fracture.…
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Physical properties
Hardness about 6.5–7 Mohs; opaque, olive-green, brown, mustard-yellow, cream, and white orbicular pattern; waxy to glossy luster after polishing; cryptocrystalline quartz with no visible cleavage and uneven fracture. The rounded white patches are characteristic spherulitic/orbicular structures, though the exact variety is uncertain from an image.
Formation & geological history
Forms when silica-rich fluids replace and cement altered volcanic or tuffaceous material, commonly producing concentric spherules; many ocean jasper specimens formed in Permian–Triassic volcanic rocks of Madagascar, while similar orbicular jaspers occur elsewhere.
Uses & applications
Used for cabochons, beads, carvings, polished palm stones, and decorative objects; valued mainly as a lapidary and collector material.
Geological facts
“Ocean jasper” is a commercial name, not a single formally defined mineral species. Orbicular patterns arise from repeated mineral growth or replacement around nucleation centers.
Field identification & locations
Identify by its very fine-grained silica body, opaque multicolor orbicules, glassy/waxy polish, and lack of cleavage; common sources include Madagascar, Mexico, Australia, and the western United States. A specific locality requires provenance or testing.
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