mineral

Orbicular jasper (possibly ocean jasper)

Microcrystalline quartz/chalcedony, SiO₂, with iron-rich and other mineral inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; gray, cream, and black concentric or flowing banding; waxy to dull luster; cryptocrystalline quartz with no visible cleavage. The rounded, polished surface appears tumbled.

Identified August 22, 2026More mineral →

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Physical properties

Hardness 6.5–7 Mohs; gray, cream, and black concentric or flowing banding; waxy to dull luster; cryptocrystalline quartz with no visible cleavage. The rounded, polished surface appears tumbled.

Formation & geological history

Forms when silica-rich volcanic fluids or sedimentary silica replace and cement host material, with rhythmic mineral precipitation producing orbicular banding. Ocean jasper is chiefly associated with Miocene volcanic rocks of Madagascar; exact age depends on locality.

Uses & applications

Used for cabochons, beads, carvings, display stones, and lapidary collectibles; generally unsuitable as a major construction stone because it is sold in small pieces.

Geological facts

The patterns result from alternating chalcedony, quartz, and iron- or manganese-bearing material, not true agate layers in every specimen. “Orbicular jasper” is a broad trade term, and visual identification cannot confirm the locality.

Field identification & locations

Identify by testing for quartz hardness, observing opaque rather than translucent bands, and checking for a glassy fracture; it should scratch glass but not be scratched by steel. Common sources include Madagascar, Oregon, Mexico, and Australia.