sedimentary

Polished ocean jasper (orbicular jasper)

Microcrystalline quartz/chalcedony with iron oxides and accessory minerals; SiO₂-dominant

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque, multicolored green, red, cream, and yellow patterning with a waxy to vitreous polish. Cryptocrystalline and typically massive, with no visible cleavage; specific gravity about 2.5–2.7.

Identified September 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when silica-rich fluids replaced or cemented volcanic rock, producing jasper and orbicular textures; the commonly sold Madagascar material is generally Mesozoic to Cenozoic in age. This specimen is tumbled and polished, so its natural surface is obscured.

Uses & applications

Used for cabochons, beads, carvings, worry stones, and decorative objects; not generally used as construction aggregate. Attractive patterning gives it modest lapidary and collector value.

Geological facts

Red coloration commonly reflects hematite, while green tones may result from chlorite, epidote, or other alteration minerals. “Ocean jasper” is a trade name rather than a single formally defined mineral species.

Field identification & locations

Identify it by its opaque chalcedony body, bright red-green-cream patches, and high polish; verify with a glass-scratch test only on an inconspicuous area. Classic orbicular ocean jasper is associated especially with remote coastal deposits of northwestern Madagascar.