mineral

Polished ocean jasper (orbicular jasper)

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

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; orange, cream, and green mottling with a waxy-to-glassy luster and no visible cleavage. The rounded, polished surface obscures its fine-grained cryptocrystalline structure; density is typically about 2.55–2.70 g/cm³.

Identified August 19, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich fluids fill cavities or replace volcanic rock, with iron and other minerals producing the colors and orbicular patterns; most classic ocean jasper formed in Oligocene–Miocene volcanic rocks. It is especially associated with rhyolitic coastal formations of northwestern Madagascar.

Uses & applications

Used for cabochons, beads, carvings, display pieces, and lapidary collections; it has little industrial value compared with ordinary quartz.

Geological facts

The orange-green pattern likely reflects iron oxides and chlorite or related green inclusions, though exact identification requires testing or microscopy. “Ocean jasper” is a trade name commonly applied to orbicular jasper from Madagascar.

Field identification & locations

Identify it by its opaque body, rounded orbicular or mossy patterns, conchoidal fracture, and resistance to scratching by steel; acid produces no reaction. Common sources include Madagascar, Oregon, Mexico, and Australia.