mineral

Smoky Quartz (Rough Specimen)

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Translucent grey to brownish-yellow; Luster: Vitreous (glassy); Crystal structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

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

Identified February 12, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Translucent grey to brownish-yellow; Luster: Vitreous (glassy); Crystal structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed in igneous and metamorphic rocks, particularly pegmatites and hydrothermal veins. The smoky coloring is caused by natural irradiation of trace aluminum impurities within the crystal lattice over millions of years.

Uses & applications

Used primarily for jewelry (faceted or cabochons), metaphysical/collector specimens, and historically for early eyeglasses in 12th century China. Higher quality pieces are used in decorative carvings.

Geological facts

Smoky quartz is the national gem of Scotland, where it is often referred to as 'Cairngorm' after the mountain range where it is found. It is one of the most common macro-crystalline varieties of quartz.

Field identification & locations

Identify in the field by its hardness (will scratch glass but not topaz), its conchoidal fracture (curved, shell-like break), and its smoke-like translucent coloring. Commonly found in granite-rich mountainous regions worldwide (e.g., Brazil, USA, Swiss Alps).

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