mineral
Tumbled brown quartz crystal (likely smoky quartz or iron-stained quartz)
Quartz, silicon dioxide (SiO₂)
AI-generated identification · may be incorrectHardness 7 Mohs; translucent brown to reddish-brown with a vitreous luster and conchoidal fracture. The rounded shape is human-tumbled, and internal color may result from irradiation, iron staining, or inclusions; cleavage is absent.
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Physical properties
Hardness 7 Mohs; translucent brown to reddish-brown with a vitreous luster and conchoidal fracture. The rounded shape is human-tumbled, and internal color may result from irradiation, iron staining, or inclusions; cleavage is absent.
Formation & geological history
Quartz crystallizes from silica-rich hydrothermal fluids, pegmatites, and igneous rocks; smoky coloration commonly develops through natural irradiation of trace aluminum. Geological ages vary widely by deposit, often millions to billions of years.
Uses & applications
Used as a decorative tumbled stone, lapidary material, and collector specimen; gem-quality transparent material can be faceted, though this small piece appears common-grade.
Geological facts
Quartz is one of Earth’s most abundant minerals and is the defining mineral of many sands and veins. Brown quartz may be sold as smoky quartz, cognac quartz, or iron-stained quartz depending on its cause of color.
Field identification & locations
Identify it by its glassy luster, lack of cleavage, conchoidal fracture, and ability to scratch ordinary glass; a definitive ID requires testing or magnification. Common sources include Brazil, Madagascar, the United States, and worldwide quartz-bearing rocks.
