mineral
Tumbled smoky quartz
Quartz (SiO₂), smoky variety
AI-generated identification · may be incorrectLikely a small polished or naturally worn quartz fragment, translucent brown-gray with vitreous luster. Mohs hardness 7; hexagonal crystal structure, no cleavage, conchoidal fracture; specific gravity about 2.65.
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Physical properties
Likely a small polished or naturally worn quartz fragment, translucent brown-gray with vitreous luster. Mohs hardness 7; hexagonal crystal structure, no cleavage, conchoidal fracture; specific gravity about 2.65.
Formation & geological history
Smoky quartz forms in silica-rich igneous and hydrothermal veins, where natural irradiation colors clear quartz brown. Crystals range from ancient Precambrian specimens to much younger hydrothermal deposits.
Uses & applications
Used as an ornamental and lapidary stone, in jewelry, carvings, and mineral collections. Common small tumbled pieces generally have modest commercial value.
Geological facts
The dark color is caused mainly by irradiation-induced color centers associated with trace aluminum. Strongly colored transparent crystals are more valuable than opaque or heavily fractured material.
Field identification & locations
Common sources include Brazil, Madagascar, Switzerland, the United States, and Scotland. Confirm with hardness testing—quartz scratches ordinary glass—while avoiding destructive tests on a collectible piece.
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