mineral

Polished ocean jasper (orbicular jasper)

Microcrystalline quartz/chalcedony, SiO₂, with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque tan, orange-brown, and dark red-brown; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage. The smooth, rounded surface indicates tumbling or polishing.

Identified August 19, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich fluids replace or fill cavities in volcanic rhyolitic rock, with iron and other minerals producing the mottled coloration. Classic ocean jasper formed in Miocene volcanic rocks of Madagascar, roughly 5–23 million years old.

Uses & applications

Used for cabochons, beads, carvings, polished stones, and lapidary collections; occasional decorative stone, but generally not a major construction material.

Geological facts

The term “ocean jasper” is a trade name commonly applied to orbicular jasper from Madagascar. Its patterns range from concentric orbs to irregular iron-rich patches, as visible here.

Field identification & locations

Identify by its opaque, fine-grained silica texture, earthy multicolor pattern, lack of cleavage, and ability to scratch glass; distinguish from agate by its generally opaque body. Common sources include Madagascar, Australia, Brazil, and Mexico.