mineral

Brown chalcedony (likely jasper or chert)

Microcrystalline quartz, SiO₂; opaque iron-oxide-rich variety

AI-generated identification · may be incorrect

Typically Mohs 6.5–7, brown to ochre, with dull to waxy luster and no visible cleavage; cryptocrystalline quartz has a very fine-grained structure. The irregular pale patches and earthy coloration suggest jasper/chert rather than transparent chalcedony.

Identified September 14, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities, fractures, or sediment pores, later becoming microcrystalline quartz; iron oxides produce the brown color. Exact age cannot be determined from the photograph and may range from Paleozoic to recent depending on locality.

Uses & applications

Used as ornamental stone, cabochons, carvings, beads, and decorative specimens; jasper and chert have also been used historically for tools and building decoration.

Geological facts

Jasper is an opaque, impurity-rich variety of chalcedony, while chert is its commonly sedimentary counterpart; the boundaries between these names are often informal.

Field identification & locations

Identify by testing for glass-scratching hardness, examining the waxy fracture, and checking that it does not fizz strongly in dilute acid. Brown jasper/chert occurs widely, including India, Madagascar, Brazil, Mexico, and the western United States.