sedimentary

Leopard jasper (orbicular jasper)

Silicified volcanic tuff/chert; predominantly microcrystalline quartz (SiO₂) with iron oxides and volcanic minerals

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque, multicolored tan, mustard-yellow, brown, black, and red-brown; dull to waxy or polished vitreous luster. The circular orbicules are silica-rich replacement or devitrification structures in a fine-grained matrix; no obvious cleavage.

Identified August 19, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when silica-rich fluids altered and silicified volcanic ash or lava, producing concentric orbicules; commonly Cenozoic in age, though exact age depends on locality. Similar material is especially associated with Madagascar and parts of Mexico and the western United States.

Uses & applications

Used as a lapidary stone for cabochons, carvings, beads, bookends, and polished slabs; valued mainly for attractive orbicular patterns rather than industrial applications.

Geological facts

The “leopard” pattern is natural and varies greatly between pieces; it is often marketed broadly as orbicular jasper, although some specimens are technically silicified rhyolitic tuff or orbicular chert.

Field identification & locations

Identify it by abundant rounded, eye-like yellow and brown orbicules in a dark siliceous matrix, plus its hardness and lack of acid reaction. Typical collector value is about $10–$50 for a hand specimen, or $50–$200 for exceptional polished pieces.