mineral

Polished ocean jasper / orbicular jasper

Microcrystalline quartz (SiO₂), commonly with chalcedony, feldspar, and iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; gray-green groundmass with pale orbicular or brecciated patches and a dull-to-waxy polished luster. Cryptocrystalline, with no visible cleavage; specific gravity about 2.6.

Identified August 24, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich volcanic fluids fill cavities and fractures, later developing spherulitic or orbicular textures through rhythmic mineral growth and alteration. Most commercial ocean jasper comes from Oligocene–Miocene volcanic rocks of Madagascar.

Uses & applications

Used for cabochons, beads, carvings, polished stones, and collector specimens; occasionally used as decorative stone. Small common pieces generally have modest value.

Geological facts

The name “ocean jasper” is primarily a trade name for orbicular jasper from Madagascar, not a single formally defined mineral species. Its circular patterns commonly reflect radiating silica or feldspar growth around alteration centers.

Field identification & locations

Identify it by its opaque, patterned, silica-rich appearance, waxy polish, and lack of strong cleavage; it should scratch glass but not be scratched by a steel knife. Common localities include Madagascar, Mexico, Oregon, and Australia.