mineral

Smoky Quartz and Chalcedony Geode Fragment

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Smoky brown, grey, and translucent tan; Luster: Vitreous to waxy; Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Smoky brown, grey, and translucent tan
Luster: Vitreous to waxy

Identified February 22, 2026More mineral →

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Physical properties

Formation & geological history

Formed in cavities or vesicles of volcanic igneous rock (like basalt) or sedimentary rock through the precipitation of silica-rich hydrothermal fluids. The 'smoky' coloration is typically caused by natural gamma irradiation from surrounding rock over millions of years.

Uses & applications

Used primarily for lapidary work, jewelry (cabochons), as metaphysical 'healing' stones, and as decorative cabinet specimens for collectors.

Geological facts

Smoky quartz gets its color from trace amounts of aluminum replacing silicon atoms in the crystal lattice, which is then activated by radiation. This specific specimen shows a botryoidal (grape-like) texture on the inner surface, common in chalcedony.

Field identification & locations

Identify by its smoky-translucent quartz crystals or waxy chalcedony surface inside a rough brown host rock. Commonly found in Brazil, Madagascar, and the USA. Collectors look for well-defined crystal points or unique 'bubbly' botryoidal structures.

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