mineral

Smoky Quartz

Smoky Quartz (Silicon Dioxide, SiO2)

Hardness: 7 on Mohs scale. Color: Translucent to opaque brownish-grey to black. Luster: Vitreous (glassy). Crystal Structure: Hexagonal/Trigonal. Cleavage: Indistinct/Conchoidal fracture. Specific Gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Translucent to opaque brownish-grey to black
Luster: Vitreous (glassy)

Identified March 16, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous and metamorphic rocks (especially granite pegmatites and hydrothermal veins). The smoky color is caused by natural irradiation of aluminum-bearing quartz over millions of years. It can be found in rocks from the Precambrian to Cenozoic eras.

Uses & applications

Commonly used as a gemstone in rings, pendants, and beads. Widely utilized in metaphysical practices and crystal collecting. Historically used by the Chinese in the 12th century to create early sunglasses.

Geological facts

The color is not caused by impurities like most gems, but rather by free silicon formed from silicon dioxide by natural irradiation. While it is the national gem of Scotland (where it is called Cairngorm), the finest specimens often come from the Swiss Alps or Brazil.

Field identification & locations

Identify in the field by its hardness (will scratch glass), glassy luster, and characteristic conchoidal (shell-like) fracture. Found globally in mountainous regions. Collectors should look for clarity and 'phantom' crystal growth inside.