mineral

Smoky Quartz Geode Cluster

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Grayish-brown, tea-colored, or black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Grayish-brown, tea-colored, or black
Luster: Vitreous (glassy)

Identified May 2, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Grayish-brown, tea-colored, or black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the crystallization of silica-rich hydrothermal fluids in cavities or volcanic vugs. The smoky color is caused by natural irradiation of trace aluminum impurities over millions of years.

Uses & applications

Primarily used as a decorative specimen for collectors, in lapidary work for jewelry, and occasionally in the gemstone industry for carvings or faceted stones.

Geological facts

Unlike many dark minerals, smoky quartz owes its color to natural radiation from surrounding rocks activating aluminum atoms in the crystal lattice. It is the national gem of Scotland, where it is known as Cairngorm.

Field identification & locations

Identify in the field by its six-sided pointed crystals, transparency, and smoky hue. Frequently found in Brazil, Madagascar, and the Swiss Alps. For collectors, look for lack of bubbles and high clarity within the darkened areas.