
mineral
Orbicular jasper (ocean jasper)
Microcrystalline quartz (SiO₂), chiefly chalcedony with feldspar, zeolites, and iron-oxide inclusions
AI-generated identification · may be incorrectPolished, opaque stone with cream-white orbicular patterns in olive-brown to gray matrix; vitreous to waxy luster, cryptocrystalline structure, no visible cleavage, Mohs hardness about 6.5–7, specific gravity ~2.6.…
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Physical properties
Polished, opaque stone with cream-white orbicular patterns in olive-brown to gray matrix; vitreous to waxy luster, cryptocrystalline structure, no visible cleavage, Mohs hardness about 6.5–7, specific gravity ~2.6. The rounded patterning is characteristic of orbicular jasper, though exact identification from an image is provisional.
Formation & geological history
Silica-rich volcanic rock was altered and replaced by chalcedony and other minerals, producing orbicules; commonly associated with Miocene volcanic formations, especially Madagascar. Geological age and locality cannot be confirmed from the photograph alone.
Uses & applications
Used for cabochons, beads, carvings, tumbled stones, and decorative objects; not generally used as a structural construction stone.
Geological facts
Ocean jasper is a trade name applied mainly to orbicular jasper from Madagascar; many visually similar orbicular jaspers are sold under the same label.
Field identification & locations
Identify by its opaque silica-rich body, polished glassy surface, hardness, and concentric or radiating orbicules; a steel file should not easily scratch it. Common sources include Madagascar, Mexico, Australia, and the United States.
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