mineral

Smoky Quartz Geode Slice

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Smoky brown to yellowish-clear; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (Trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Smoky brown to yellowish-clear
Luster: Vitreous (glassy)

Identified April 16, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Smoky brown to yellowish-clear; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (Trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific Gravity: 2.65

Formation & geological history

Formed through hydrothermal processes in cavities within igneous rocks or volcanic geodes. The smoky color is usually the result of natural irradiation of trace aluminum within the quartz crystal lattice.

Uses & applications

Primarily used as decorative display specimens, collector items, and in metaphysical practices. High-quality smoky quartz is also used in jewelry and lapidary arts.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm'. The dark color is caused by the exposure of the quartz to natural radiation from surrounding granite and other minerals over millions of years.

Field identification & locations

Identify in the field by its crystal habit, its 7 hardness (it will scratch glass), and its distinct semi-transparent smoky color. Commonly found in Brazil, Madagascar, and the United States (Colorado).