Smoky Quartz

Physical Properties

Hardness: 7 (Mohs scale); Color: Brownish-grey, smoky-black, to translucent; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: Indistinct; 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

Primary use is in jewelry as a gemstone, ornamental carvings, and occasionally in the manufacturing of optical instruments or pressure sensors due to piezoelectric properties.

Geological Facts

Smoky Quartz is the national gem of Scotland, where it is known as 'Cairngorm'. In ancient China, thin slices of smoky quartz were used to make the world's first sunglasses.

Field Identification & Locations

Identify by its characteristic 'smoke' color and glass-like luster. It is commonly found in areas with granite such as the Swiss Alps, Brazil, and the United States (Colorado). To identify in the field, check for crystal habit and hardness (it should scratch glass).

Identified on: 4/26/2026

Mode: Standard