Smoky Quartz

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 distinctive color comes from free silicon formed from silicon dioxide by natural irradiation of the crystal long after its formation.

Uses & Applications

Commonly used in jewelry as a gemstone, decorative carvings, metaphysical collections, and historically in early 12th-century Chinese sunglasses made of flat panes.

Geological Facts

The dark color is caused by the exposure to natural radiation from surrounding rocks like granite. When heated, smoky quartz can lose its color or turn yellowish like citrine.

Field Identification & Locations

Identify in the field by its hexagonal crystal habit, lack of cleavage, and its ability to scratch glass (Hardness 7). Look for it in quartz veins or granite voids. Notable locations include Brazil, Scotland (Cairngorm Mountains), and Colorado, USA.

Identified on: 4/16/2026

Mode: Standard