mineral

Polished ocean jasper or orbicular chalcedony

Microcrystalline quartz (SiO₂), likely chalcedony with feldspar or other mineral inclusions

AI-generated identification · may be incorrect

Cream to gray, opaque, smoothly tumbled surface with dark branching inclusions and subtle orbicular patterning; vitreous to waxy luster. Mohs hardness about 6.5–7; no obvious cleavage; specific gravity approximately 2.6.

Identified August 8, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich fluids fill cavities or replace volcanic rock, producing chalcedony and contrasting mineral inclusions. Ocean jasper is mainly associated with Oligocene volcanic rocks of Madagascar, roughly 23–34 million years old.

Uses & applications

Used for cabochons, beads, carvings, polished stones, and lapidary collections; its durability makes it suitable for jewelry and ornamental objects.

Geological facts

The term “ocean jasper” is a trade name, not a single precisely defined mineral species. Orbicular patterns and dark dendritic inclusions can also occur in other chalcedony varieties, so exact identification may require microscopy or testing.

Field identification & locations

Identify it by its fine-grained, non-cleaving silica body, waxy polish, and patterned inclusions; a quartz scratch test should leave a mark on glass. Common sources include Madagascar, Indonesia, Mexico, and Brazil.