mineral
Tumbled brown quartz (likely iron-stained quartzite or chalcedony)
Quartz, SiO₂; possibly microcrystalline quartz (chalcedony)
AI-generated identification · may be incorrectHardness 7 Mohs; translucent brown to honey-brown, with vitreous to waxy luster and no visible cleavage. The rounded, glossy form indicates tumbling; inclusions or iron oxides likely produce the color.
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Physical properties
Hardness 7 Mohs; translucent brown to honey-brown, with vitreous to waxy luster and no visible cleavage. The rounded, glossy form indicates tumbling; inclusions or iron oxides likely produce the color.
Formation & geological history
Quartz crystallizes from silica-rich hydrothermal fluids or igneous rocks; chalcedony forms when silica precipitates in cavities and fractures. The specimen’s original geological age cannot be determined visually and depends on its source rock.
Uses & applications
Used as a lapidary and decorative stone, in carvings, jewelry, and collections; quartz is also important industrially in glass, ceramics, electronics, and abrasives.
Geological facts
Brown coloration commonly results from iron-oxide staining or microscopic inclusions. A true quartz specimen should scratch ordinary glass but not be scratched by a steel knife.
Field identification & locations
Commonly found in hydrothermal veins, cavities in volcanic rocks, and quartz-rich metamorphic rocks worldwide, including Brazil, Madagascar, India, and the United States. Visual identification is uncertain without a hardness or specific-gravity test.
