metamorphic
Leopard jasper (orbicular jasper)
Silicified volcanic rock, chiefly microcrystalline quartz/chalcedony (SiO₂) with feldspar and iron-oxide inclusions
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; cream, gray, brown, and black orbicular pattern; vitreous to waxy luster; cryptocrystalline, massive, with no visible cleavage. The polished cabochon shows dark circular inclusions in a lighter matrix.
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Physical properties
Hardness about 6.5–7 Mohs; cream, gray, brown, and black orbicular pattern; vitreous to waxy luster; cryptocrystalline, massive, with no visible cleavage. The polished cabochon shows dark circular inclusions in a lighter matrix.
Formation & geological history
Forms when silica-rich fluids silicify and replace volcanic ash or rhyolitic/tuffaceous rock, producing orbicular patterns; commonly considered a low-grade metamorphic or hydrothermal siliceous rock, generally of Cenozoic or older volcanic age.
Uses & applications
Used for cabochons, beads, carvings, lapidary décor, and small collectible specimens; rarely used architecturally because it is decorative but not uniform.
Geological facts
The distinctive “leopard spots” are orbicules or altered mineral/inclusion zones, not animal markings. Commercial material is especially associated with Mexico, Indonesia, Madagascar, and parts of the western United States.
Field identification & locations
Identify by its opaque cream matrix, rounded dark spots, silica-like hardness, and ability to take a high polish; it should resist scratching by a steel knife. Avoid confusing it with spotted rhyolite or manufactured glass.
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