metamorphic
Orbicular jasper (likely brecciated jasper)
Microcrystalline quartz/chalcedony (SiO₂) with iron-oxide and silica-rich clasts
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; brown, tan, cream, and reddish colors with an orbicular/brecciated pattern; generally dull to waxy or slightly vitreous luster. Cryptocrystalline quartz has no visible cleavage and conchoidal fracture; typical specific gravity is 2.55–2.70.
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Physical properties
Hardness about 6.5–7 Mohs; brown, tan, cream, and reddish colors with an orbicular/brecciated pattern; generally dull to waxy or slightly vitreous luster. Cryptocrystalline quartz has no visible cleavage and conchoidal fracture; typical specific gravity is 2.55–2.70.
Formation & geological history
Formed when silica-rich fluids cemented and altered rounded or fractured rock fragments, with iron oxides producing the earthy colors; the exact geological age depends on locality. It is commonly associated with volcanic terrains and hydrothermal activity.
Uses & applications
Used for polished cabochons, carvings, beads, bookends, and decorative stone; occasionally sold as a lapidary rough. It has little structural or industrial use.
Geological facts
Orbicular jasper is prized for concentric or eye-like patterns, though similar-looking material may be brecciated jasper or silicified volcanic rock. The specimen appears water-worn or polished, which accentuates its pattern.
Field identification & locations
Identify it by its opaque appearance, quartz-like hardness, waxy luster, and inability to scratch with a steel knife easily; it should not fizz in dilute hydrochloric acid. Common sources include Madagascar, Mexico, Oregon, Indonesia, and Australia.
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