mineral
Dendritic jasper (brecciated or orbicular jasper)
Microcrystalline quartz (SiO₂) with iron-oxide inclusions
AI-generated identification · may be incorrectOpaque tan, cream, and reddish-brown matrix with dark branching or mottled iron-oxide patterns; typically Mohs 6.5–7, vitreous to waxy luster, cryptocrystalline structure, no visible cleavage, and specific gravity around 2.6. The photographed piece appears naturally rough or lightly polished.
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Physical properties
Opaque tan, cream, and reddish-brown matrix with dark branching or mottled iron-oxide patterns; typically Mohs 6.5–7, vitreous to waxy luster, cryptocrystalline structure, no visible cleavage, and specific gravity around 2.6. The photographed piece appears naturally rough or lightly polished.
Formation & geological history
Forms when silica-rich fluids replace or cement volcanic ash, sediments, or fractured rock, while iron and manganese oxides create the brown dendritic markings. Jasper deposits are commonly Paleozoic to Cenozoic, though exact age depends on locality.
Uses & applications
Used as an ornamental stone, cabochon material, beads, carvings, and tumbled stone; occasionally used for decorative slabs. Common material generally has modest commercial value.
Geological facts
Dendritic patterns are mineral inclusions or replacement textures, not fossils or plant remains. The specimen may also be marketed locally as picture jasper if the pattern suggests a landscape.
Field identification & locations
Commonly found in volcanic and sedimentary terrains, including Oregon, Idaho, Utah, Madagascar, Brazil, and Australia. Verify with a hardness test: it should scratch ordinary glass; acid produces no reaction.
