mineral

Smoky Quartz

Quartz (Silicon Dioxide) - SiO2

Hardness: 7 on Mohs scale; Color: Translucent grey to brownish-black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

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

Identified March 8, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Translucent grey to brownish-black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed in igneous and metamorphic rocks, particularly pegmatites and hydrothermal veins. The smoky color is caused by natural irradiation of aluminum-bearing quartz over millions of years.

Uses & applications

Used in jewelry as gemstones, in decorative carvings, and as popular mineral specimens for collectors. Historically used in early Chinese sunglasses in the 12th century.

Geological facts

The dark color is unstable at high temperatures; heating smoky quartz can turn it yellow (creating 'burnt amethyst' or citrine-like colors). It is the national gem of Scotland, where it is known as 'Cairngorm'.

Field identification & locations

Identify in the field by its hardness (scratches glass), lack of cleavage, and translucent 'smoky' appearance. Commonly found in mountainous regions like the Alps, Brazil, Colorado (Pikes Peak), and Scotland.