mineral

Orbicular jasper (likely ocean jasper)

Silica-rich microcrystalline quartz/chalcedony with feldspar and accessory minerals; composition varies

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque gray, cream, and dark green-black orbicular patterns; waxy to dull luster; microcrystalline, with no obvious cleavage; specific gravity roughly 2.5–2.7.

Identified August 8, 2026More mineral →

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Physical properties

Hardness about 6.5–7 Mohs; opaque gray, cream, and dark green-black orbicular patterns; waxy to dull luster; microcrystalline, with no obvious cleavage; specific gravity roughly 2.5–2.7.

Formation & geological history

Forms when silica-rich volcanic fluids or lava develop concentric mineral growths and are later silicified. Ocean jasper is chiefly associated with Oligocene–Miocene volcanic rocks of Madagascar, though similar orbicular jaspers occur worldwide.

Uses & applications

Used for cabochons, beads, carvings, polished stones, and mineral collections; occasionally sold as decorative lapidary material.

Geological facts

The distinctive “orb” pattern consists of concentric zones of chalcedony, quartz, feldspar, and iron- or manganese-bearing minerals. The pictured rounded, polished specimen strongly resembles orbicular jasper, but exact identification requires locality or testing.

Field identification & locations

Look for opaque stone with rounded or concentric spherulitic markings, a glassy-to-waxy surface, and no fizz in dilute acid; it should scratch glass. Common sources include Madagascar, Mexico, Australia, and the United States.