Smoky Quartz

Physical Properties

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

Formation & Geological History

Formed in igneous or metamorphic rocks (such as granite pegmatites) through the natural irradiation of aluminum-containing quartz. It can take millions of years for the color to develop.

Uses & Applications

Used in gemstone jewelry, ornamental carvings, and as a popular specimen for mineral collectors. Historically used in early Chinese sunglasses.

Geological Facts

The brown color is produced when natural radiation from surrounding rocks interacts with trace amounts of aluminum within the quartz crystal lattice. It is the national gem of Scotland.

Field Identification & Locations

Identify in the field by its hardness (scratches glass), lack of cleavage, and translucent brown color. Commonly found in Brazil, USA (Colorado), Switzerland, and Madagascar.

Identified on: 4/25/2026

Mode: Standard