mineral

Smoky Quartz (Polished)

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Gray, brown, to black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Gray, brown, to black
Luster: Vitreous (glassy)

Identified April 26, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Gray, brown, to black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65.

Formation & geological history

Formed in igneous or metamorphic environments, primarily in pegmatites and hydrothermal veins. The smoky color is caused by natural irradiation of trace aluminum impurities within the quartz.

Uses & applications

Used primarily in lapidary work, cabochons for jewelry, ornamental decorations, and as a popular specimen for mineral collectors.

Geological facts

Smoky Quartz is the national gem of Scotland, where it is known as 'Cairngorm'. In ancient China, it was used to create the earliest known sunglasses to hide a judge's facial expressions.

Field identification & locations

Identify by its hardness (scratches glass), glassy luster, and translucent to transparent grayish-brown hue without streaks. Common in Brazil, Madagascar, and the USA (Colorado).