mineral
Tumbled brown chalcedony or jasper
Microcrystalline quartz, SiO₂; likely iron-oxide-bearing chalcedony/jasper
AI-generated identification · may be incorrectSmall rounded, semi-opaque brown-and-gray specimen with a waxy to weakly vitreous luster; quartz hardness is about 7 Mohs, with no visible cleavage and conchoidal fracture. The brown color likely comes from iron oxides; exact identification requires testing.
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Physical properties
Small rounded, semi-opaque brown-and-gray specimen with a waxy to weakly vitreous luster; quartz hardness is about 7 Mohs, with no visible cleavage and conchoidal fracture. The brown color likely comes from iron oxides; exact identification requires testing.
Formation & geological history
Forms when silica-rich groundwater fills cavities, fractures, or pores and crystallizes as microcrystalline quartz, often with iron staining. Such material commonly formed in volcanic or sedimentary environments over a wide range of geologic ages.
Uses & applications
Used for inexpensive cabochons, beads, carvings, tumbled stones, and lapidary practice; larger attractive pieces may be collectible. This small specimen has modest commercial value.
Geological facts
Jasper is opaque and impurity-rich, whereas chalcedony is more translucent; the pictured piece may be an intermediate or mixed material. Color and polish alone cannot reliably distinguish it from brown agate or iron-stained quartz.
Field identification & locations
Common in volcanic terrains, river gravels, and silica-rich sedimentary deposits worldwide, including Brazil, India, Madagascar, Mexico, and the western United States. Check for glassy conchoidal fracture, lack of cleavage, and inability to scratch it with a steel knife; a scratch test should be performed inconspicuously.
