mineral
Smoky quartz (likely rough or tumbled fragment)
Quartz, silicon dioxide (SiO₂), brown variety colored by irradiation and trace aluminum
AI-generated identification · may be incorrectTypically Mohs hardness 7, brown to gray-brown, vitreous luster, translucent to transparent, with a hexagonal crystal structure and indistinct cleavage; conchoidal fracture and specific gravity about 2.65. The pictured piece appears dark brown, translucent, and naturally fractured or lightly polished.
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Physical properties
Typically Mohs hardness 7, brown to gray-brown, vitreous luster, translucent to transparent, with a hexagonal crystal structure and indistinct cleavage; conchoidal fracture and specific gravity about 2.65. The pictured piece appears dark brown, translucent, and naturally fractured or lightly polished.
Formation & geological history
Forms in silica-rich igneous and hydrothermal environments, especially granite pegmatites and alpine veins; specimens range from Precambrian to recent geological ages. Common localities include Brazil, Switzerland, Madagascar, the United States, and Scotland.
Uses & applications
Used as a lapidary and jewelry stone, ornamental material, and mineral specimen; clear smoky quartz can be faceted, while fractured pieces are commonly collected.
Geological facts
Its color is generally produced by natural radiation acting on trace aluminum impurities; heating can fade or alter the color. Exact identification from the photograph is somewhat limited because very dark brown obsidian or quartz-rich material can look similar.
Field identification & locations
Look for glassy luster, conchoidal fracture, translucency, and hardness sufficient to scratch ordinary glass; quartz lacks obvious cleavage. Estimated value is about $2–$20 for a small common fragment, or $25–$200+ for attractive, well-formed crystals.
