mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Gray, brownish to black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Gray, brownish to black
Luster: Vitreous (glassy)

Identified May 25, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 7 on Mohs scale; Color: Gray, brownish to black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific Gravity: 2.65

Formation & geological history

Forms in igneous rocks like granite or metamorphic rocks like gneiss. The color is caused by natural gamma radiation activating color centers around aluminum impurities within the crystal lattice.

Uses & applications

Used in jewelry for gemstones, metaphysical healing practices, decorative carvings, and historically in early sunglasses and optical instruments.

Geological facts

Smoky quartz is the national gem of Scotland, where it is often referred to as 'Cairngorm' after the mountain range where it is found. It can range from nearly transparent to opaque black (known as Morion).

Field identification & locations

Identify in the field by its distinct smoky color reaching through the crystal, its ability to scratch glass, and its conchoidal (shell-like) fracture pattern. It is commonly found in pegmatites and Alpine-type veins.