Smoky Quartz

Physical Properties

Hardness: 7 on Mohs scale; Color: Grayish-brown to black translucency; Luster: Vitreous (glassy); Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Formation & Geological History

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

Uses & Applications

Used primarily in jewelry (faceting and cabochons), as ornamental specimens for collectors, and in metaphysical practices. Historically used in China for sunglasses in the 12th century.

Geological Facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm.' Large crystals weighing hundreds of pounds have been found in the Swiss Alps and Brazil.

Field Identification & Locations

Identify by its characteristic smoky transparency and conchoidal (shell-like) fractures. It is commonly found in mountainous regions like the Pike's Peak area of Colorado, the Swiss Alps, and Minas Gerais, Brazil.

Identified on: 4/15/2026

Mode: Standard