Polished ocean jasper

Hardness about 6.5–7 Mohs; opaque green, brown, cream, and reddish zones with a vitreous-to-waxy polish, orbicular patterns, cavities, and no visible cleavage. Specific gravity is typically 2.5–2.7.

Formed when silica-rich volcanic fluids filled cavities and fractures in altered rhyolitic volcanic rock, producing chalcedony, quartz, and colorful iron- or manganese-rich patterns. Most classic material formed in Madagascar, likely during Mesozoic volcanic activity.

Used for ornamental carvings, polished freeforms, cabochons, beads, and collector specimens; it has little structural or industrial use beyond decorative stone.

The name “ocean jasper” is a trade name, not a single formally defined mineral species. Its distinctive circles and flowing patterns result from repeated silica deposition, brecciation, and mineral replacement.

Identify it by its opaque multicolor orbicular or scenic patterns, smooth polish, and quartz-like hardness; common localities include northwest Madagascar, especially the remote Marovato region. Acid and scratch testing should be avoided on finished pieces.