sedimentary

Polished ocean jasper (orbicular jasper)

Orbicular jasper; chiefly microcrystalline quartz (SiO₂) with chalcedony, iron oxides, and accessory minerals

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque cream, green, gray, and reddish-brown orbicular patterns; dull to vitreous polish; cryptocrystalline quartz with no cleavage, conchoidal fracture, and specific gravity around 2.55–2.70.

Identified August 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when silica-rich volcanic or hydrothermal fluids cemented and replaced volcanic ash or lava, producing concentric orbicules and brecciation. Most commercially known ocean jasper comes from Miocene–Tertiary volcanic rocks near the coast of northwestern Madagascar.

Uses & applications

Primarily used for cabochons, spheres, beads, carvings, and ornamental objects; valued as a decorative lapidary stone rather than for industrial construction.

Geological facts

The name “ocean jasper” is a trade name, not a single rigorously defined mineral species; orbicular patterns distinguish it from ordinary jasper and agate.

Field identification & locations

Identify it by its opaque body, rounded cream/green/red orbicules, and quartz-like hardness; glass is scratched by quartz, while jasper does not show translucent banding typical of many agates. Common sources include Madagascar, Mexico, Australia, and Oregon.