mineral

Polished ocean jasper (likely orbicular jasper)

Microcrystalline quartz/chalcedony (SiO₂) with iron-oxide and other mineral inclusions

AI-generated identification · may be incorrect

Opaque, polished, dark green-gray to reddish-brown with mottled inclusions; vitreous to waxy luster and no visible cleavage. Mohs hardness about 6.5–7; cryptocrystalline structure; specific gravity roughly 2.5–2.7.

Identified August 23, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich fluids fill cavities or replace volcanic rock, with iron and other minerals creating the mottled colors; most ocean jasper formed in Oligocene–Miocene volcanic rocks, approximately 5–30 million years old.

Uses & applications

Used for cabochons, carvings, jewelry, polished specimens, and ornamental objects. This appears to be a tumbled or shaped cabochon.

Geological facts

The exact variety is difficult to confirm from one photograph; similar material may be labeled ocean jasper, kambaba jasper, or simply polychrome jasper.

Field identification & locations

Identify by its opaque chalcedony body, glassy polish, hardness, and lack of cleavage; it should not scratch easily with a steel knife. Ocean jasper is famously associated with Madagascar, while similar jasper occurs worldwide.