mineral
Tumbled brown jasper (likely orbicular or brecciated jasper)
Jasper, microcrystalline quartz/chalcedony; SiO₂
AI-generated identification · may be incorrectOpaque, smoothly polished, brown to mustard with dark mottling and possible subtle brecciation; typically dull to waxy luster and no visible crystal faces. Mohs hardness 6.5–7, conchoidal fracture, specific gravity about 2.55–2.70; cleavage absent.
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Physical properties
Opaque, smoothly polished, brown to mustard with dark mottling and possible subtle brecciation; typically dull to waxy luster and no visible crystal faces. Mohs hardness 6.5–7, conchoidal fracture, specific gravity about 2.55–2.70; cleavage absent.
Formation & geological history
Forms when silica-rich groundwater replaces or cements volcanic ash, sediments, or rock fragments, often incorporating iron oxides that create brown, red, and yellow colors. Deposits range from Precambrian to recent, depending on locality.
Uses & applications
Used as a lapidary stone for tumbled stones, cabochons, carvings, beads, and ornamental objects; also collected as an attractive common gemstone.
Geological facts
Jasper is a variety of opaque chalcedony or microcrystalline quartz rather than a single precisely defined mineral species. Iron staining commonly produces its warm brown coloration.
Field identification & locations
Identify it by opacity, fine-grained texture, strong polish, hardness, and lack of cleavage; it should scratch glass but not be scratched by a steel knife. Common sources include the western United States, Madagascar, Brazil, India, and Australia.
