mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale. Color: Brown to black, smoky gray. Luster: Vitreous (glassy). Crystal Structure: Hexagonal (trigonal). Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Brown to black, smoky gray
Luster: Vitreous (glassy)

Identified July 8, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale. Color: Brown to black, smoky gray. Luster: Vitreous (glassy). Crystal Structure: Hexagonal (trigonal). Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Formation & geological history

Formed in igneous or metamorphic rocks, particularly pegmatites and hydrothermal veins. The smoky color is caused by natural gamma radiation from surrounding rock that activates aluminum impurities within the crystal lattice.

Uses & applications

Used widely in jewelry (faceted or cabochons), ornamental carvings, and decorative displays. It is also used in oscillator plates for electronics due to its piezoelectric properties, though synthetic quartz is now more common.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm' after the Cairngorm Mountains. Extremely dark, opaque specimens are often referred to as 'Morion'.

Field identification & locations

Identify by its glassy luster, lack of cleavage, and characteristic translucent 'smoke' color. It is common in mountainous regions like the Alps, Brazil, and the United States (Colorado and New Hampshire).