mineral

Orbicular ocean jasper (likely)

Silicified volcanic rhyolite; chiefly microcrystalline quartz (SiO₂), with feldspar and chlorite/epidote alteration minerals

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; blue-gray, white, and green-black orbicular pattern; waxy to vitreous luster when polished; very fine-grained, massive, with no visible cleavage. The rounded polished shape indicates a tumbled or cut specimen.

Identified September 12, 2026More mineral →

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Physical properties

Formation & geological history

Forms from silica-rich volcanic flows, commonly by replacement and devitrification of rhyolite, with spherulitic/orbicular textures developing during cooling and alteration. Classic ocean jasper is Oligocene–Miocene in age and comes from coastal Madagascar, though similar orbicular jasper occurs elsewhere.

Uses & applications

Used for cabochons, beads, carvings, display stones, and lapidary work; not generally used as structural stone. Common polished pieces sell for roughly $10–$60, while unusually vivid, rare-patterned Madagascar material may reach $100–$300.

Geological facts

The image strongly suggests orbicular ocean jasper, but exact identification requires locality or testing because orbicular rhyolite, jasper, and chlorite-rich stones can look similar.

Field identification & locations

Look for concentric or radiating spherules, opaque-to-translucent silica, glassy fracture, and absence of cleavage; it should resist scratching by a steel knife. Common sources include Madagascar, Mexico, Oregon, and Australia; avoid assuming locality from appearance alone.