mineral

Polished orbicular ocean jasper

Silicified volcanic rock; chiefly microcrystalline quartz (SiO₂) with feldspar, chlorite, and iron-oxide inclusions

AI-generated identification · may be incorrect

Mohs hardness about 6.5–7; opaque, blue-green, cream, pink, brown, and black orbicular pattern; waxy to vitreous luster; cryptocrystalline quartz with no cleavage; specific gravity about 2.6–2.7.

Identified August 10, 2026More mineral →

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Physical properties

Mohs hardness about 6.5–7; opaque, blue-green, cream, pink, brown, and black orbicular pattern; waxy to vitreous luster; cryptocrystalline quartz with no cleavage; specific gravity about 2.6–2.7.

Formation & geological history

Formed when silica-rich fluids replaced or filled cavities in volcanic rhyolitic rock, producing concentric orbicules and colorful mineral inclusions. Madagascar ocean jasper is generally Cenozoic, roughly 10–30 million years old.

Uses & applications

Used as a cabochon, carving, palm stone, and lapidary collectible; unsuitable for major construction because it is decorative and occurs in limited nodules.

Geological facts

Ocean jasper is famous for its rounded orb patterns and was historically collected mainly from coastal outcrops near Marovato, Madagascar, often accessible only at low tide.

Field identification & locations

Identify it by its polished waxy surface, multicolored orbicular patterns, and hardness sufficient to scratch glass. Common localities include Madagascar; similar orbicular rhyolites occur elsewhere and may be sold under trade names.