metamorphic
Tumbled orbicular jasper
Orbicular jasper (microcrystalline quartz/chalcedony with iron-bearing minerals)
AI-generated identification · may be incorrectTypically opaque cream, tan, black, and gray with rounded orb-like patterns; Mohs hardness about 6.5–7, vitreous to waxy luster, cryptocrystalline structure, and no visible cleavage. The pictured polished pebble is consistent with orbicular jasper, though exact identification requires testing.
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Physical properties
Typically opaque cream, tan, black, and gray with rounded orb-like patterns; Mohs hardness about 6.5–7, vitreous to waxy luster, cryptocrystalline structure, and no visible cleavage. The pictured polished pebble is consistent with orbicular jasper, though exact identification requires testing.
Formation & geological history
Forms when silica-rich volcanic material is altered and develops concentric mineral aggregates; many specimens are associated with Jurassic–Cretaceous volcanic terrains, depending on locality. Common sources include Madagascar, Mexico, Oregon, and Indonesia.
Uses & applications
Used for lapidary cabochons, beads, carvings, worry stones, and decorative objects; generally ornamental rather than industrial.
Geological facts
“Orbicular” patterns result from spherulitic or concentric growth, often involving quartz, feldspar, chlorite, hematite, or other alteration minerals. Patterns vary greatly between deposits.
Field identification & locations
Identify by its opaque, multicolored orb patterns, glassy polish, and resistance to scratching by steel; it should not fizz in dilute acid. Common tumbled pieces sell for about $3–$15; larger, vividly patterned specimens may bring $20–$100+.
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