mineral
Tumbled smoky quartz (probable)
Quartz, silicon dioxide (SiO₂), smoky variety
AI-generated identification · may be incorrectHardness 7 Mohs; translucent smoky brown to gray, with a vitreous luster and conchoidal fracture rather than cleavage. The rounded, glossy surfaces indicate tumbling or polishing; exact identification is limited by the photograph.
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Physical properties
Hardness 7 Mohs; translucent smoky brown to gray, with a vitreous luster and conchoidal fracture rather than cleavage. The rounded, glossy surfaces indicate tumbling or polishing; exact identification is limited by the photograph.
Formation & geological history
Smoky quartz forms when natural radiation creates color centers in quartz, commonly in granitic pegmatites, hydrothermal veins, and cavities. Crystallization is generally associated with Precambrian to younger igneous activity, depending on locality.
Uses & applications
Used as a collectible and ornamental gemstone; transparent pieces may be faceted, while opaque or included material is commonly tumbled. It has little industrial value compared with ordinary quartz.
Geological facts
Smoky coloration can fade with strong heating or sunlight, and very dark material may be artificially irradiated. The specimen could alternatively be brown glass or another quartz variety without hardness or refractive-index testing.
Field identification & locations
Test for quartz by checking that it scratches ordinary glass but is not scratched by a steel blade; inspect for curved conchoidal fracture and possible hexagonal crystal remnants. Common sources include Brazil, Switzerland, the United States, Madagascar, and Scotland.
