mineral

Polished ocean jasper

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

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque green-gray with cream orbicular patches and a vitreous-to-waxy polished luster. It has a cryptocrystalline quartz structure, no visible cleavage, and typical specific gravity near 2.6.

Identified August 29, 2026More mineral →

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Physical properties

Formation & geological history

A volcanic silica-rich rock formed when chalcedony and quartz filled cavities in rhyolitic lava, with later mineral inclusions producing the orbicular pattern. Classic ocean jasper formed in Oligocene–Miocene volcanic rocks of Madagascar, roughly 5–30 million years old.

Uses & applications

Used mainly for cabochons, beads, carvings, polished palm stones, and decorative objects; it is not a major industrial stone.

Geological facts

The name “ocean jasper” is a trade name for orbicular jasper varieties, especially those from Madagascar. The circular patterns are mineral-filled spherulites or cavity structures, not fossils.

Field identification & locations

Identify it by its polished green-gray body, cream orbs, opaque appearance, and quartz-like hardness; it should resist scratching by a steel knife but scratch glass. Common sources include Madagascar, Mexico, Australia, and the western United States.