mineral

Polished orbicular jasper (likely ocean jasper)

Silicified microcrystalline quartz/chalcedony; mainly SiO₂ with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; dark brown to black polished matrix containing cream-to-pink rounded orbicules, with vitreous to waxy luster and no visible cleavage. Dense, opaque, and fine-grained rather than visibly crystalline.

Identified August 16, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich fluids replace volcanic or sedimentary material, producing chalcedony/quartz and iron-oxide-rich orbicular textures. Ocean jasper is especially associated with Miocene volcanic rocks of Madagascar, though similar orbicular jaspers occur worldwide.

Uses & applications

Used for cabochons, beads, carvings, polished stones, and collectors’ specimens; it has little industrial value compared with ordinary quartz.

Geological facts

The rounded spots are orbicules, formed by concentric mineral growth or replacement around nucleation centers. “Ocean jasper” is a trade name, and many visually similar stones are sold simply as orbicular jasper.

Field identification & locations

Identify it by its opaque silica-rich body, high polish, rounded contrasting orbs, and resistance to scratching by steel. Common sources include Madagascar, Mexico, Oregon, Indonesia, and Australia.