mineral
Tumbled brown banded jasper
Microcrystalline quartz (SiO₂), commonly chalcedony with iron-oxide inclusions
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; opaque brown, gold, and reddish bands with a smooth, waxy to dull luster. Massive, cryptocrystalline structure with no visible cleavage; specific gravity approximately 2.5–2.7.
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Physical properties
Hardness about 6.5–7 Mohs; opaque brown, gold, and reddish bands with a smooth, waxy to dull luster. Massive, cryptocrystalline structure with no visible cleavage; specific gravity approximately 2.5–2.7.
Formation & geological history
Forms when silica-rich groundwater fills cavities or replaces volcanic and sedimentary material, while iron oxides create the brown and red banding. Individual deposits range from Paleozoic to Cenozoic in age.
Uses & applications
Used for cabochons, beads, carvings, ornaments, and lapidary specimens; occasionally marketed as picture jasper or scenic jasper. Common tumbled pieces have modest commercial value.
Geological facts
The specimen appears polished or tumbled, so its rounded shape and glossy surface are human-processed rather than natural weathering features.
Field identification & locations
Identify by its opaque, fine-grained texture, curved or irregular iron-colored banding, lack of large crystals, and inability to scratch it easily with a steel knife. Common sources include Brazil, India, Madagascar, Australia, Mexico, and the western United States.
