mineral
Polished ocean jasper (orbicular jasper)
Jasper, microcrystalline quartz (SiO₂), commonly with iron oxides and chalcedony
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; opaque brown, cream, and reddish coloration with earthy to silky luster. It is cryptocrystalline, lacks visible cleavage, and has specific gravity near 2.6.
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Physical properties
Hardness about 6.5–7 Mohs; opaque brown, cream, and reddish coloration with earthy to silky luster. It is cryptocrystalline, lacks visible cleavage, and has specific gravity near 2.6.
Formation & geological history
A volcanic silica-rich rock formed when chalcedony and quartz filled cavities or replaced material in ancient volcanic flows, with iron oxides producing the brown-red colors. Classic orbicular material formed in the Miocene of Madagascar, roughly 5–20 million years ago.
Uses & applications
Used for cabochons, beads, carvings, polished display stones, and lapidary collections; it has little structural or industrial use.
Geological facts
The rounded polished form and contrasting rusty matrix are typical of jasper, though distinct orbicular patterns are subtle or absent in this specimen.
Field identification & locations
Identify by its opaque, dense appearance, waxy-to-dull luster, conchoidal fracture, and resistance to scratching by steel; it should not fizz in dilute acid. Common sources include Madagascar, Mexico, India, Brazil, and the western United States.
