Smoky Quartz

Physical Properties

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

Formation & Geological History

Formed in igneous or metamorphic environments, particularly pegmatites and hydrothermal veins. The smoky color results from natural irradiation and the presence of trace aluminum impurities within the crystal lattice.

Uses & Applications

Used in jewelry (gemstones), decorative carvings, and as a popular specimen for mineral collectors. Some industrial use in electronics, though synthetic quartz is more common.

Geological Facts

Smoky quartz is the national gem of Scotland, where it is often called 'Cairngorm.' It is one of the few brown gemstones that is widely and affordably available.

Field Identification & Locations

Identify in the field by its distinct smoky transparency, hexagonal crystal habit (if preserved), and the fact that it can scratch glass but cannot be scratched by a steel knife. Commonly found in granite-rich mountainous regions.

Identified on: 4/13/2026

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