metamorphic
Orbicular jasper (likely ocean jasper)
Silica-rich chalcedony/quartz with hematite- or feldspar-rich orbicules; commonly marketed as Ocean Jasper
AI-generated identification · may be incorrectDark green-gray, fine-grained and opaque, with pink-red to orange rounded patches and occasional gray chalcedony zones; Mohs hardness about 6.5–7, vitreous to waxy luster, cryptocrystalline quartz, no cleavage, specific gravity about 2.6. The rounded contrasting spots are characteristic orbicules.
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Physical properties
Dark green-gray, fine-grained and opaque, with pink-red to orange rounded patches and occasional gray chalcedony zones; Mohs hardness about 6.5–7, vitreous to waxy luster, cryptocrystalline quartz, no cleavage, specific gravity about 2.6. The rounded contrasting spots are characteristic orbicules.
Formation & geological history
Forms when silica-rich volcanic material is altered and cemented, with concentric mineral growth producing orbicules; most Ocean Jasper comes from Miocene volcanic rocks of Madagascar, roughly 5–23 million years old. Exact locality cannot be confirmed from the photograph.
Uses & applications
Cut and polished for cabochons, beads, carvings, spheres, and ornamental objects; valued primarily as a decorative lapidary stone rather than for industrial use.
Geological facts
Ocean Jasper is a trade name, not a single rigorously defined mineral species; patterns and colors vary dramatically between Madagascar seams.
Field identification & locations
Identify by testing for quartz-like hardness, dense weight, waxy polish, and rounded pink-red orbicules in a dark matrix; common sources include Madagascar, Mexico, Australia, and the western United States. Typical polished-tumbled value is $5–$30; attractive larger pieces or cabochons may sell for $30–$200+.
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