mineral
Smoky Quartz
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: Brownish grey to black, Luster: Vitreous (glassy), Crystal system: Hexagonal (trigonal), Cleavage: None (conchoidal fracture), Specific gravity: 2.65
Identified More mineral →
Explore Smoky Quartz in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale), Color: Brownish grey to black, Luster: Vitreous (glassy), Crystal system: Hexagonal (trigonal), Cleavage: None (conchoidal fracture), Specific gravity: 2.65
Formation & geological history
Forms in igneous and metamorphic rocks, particularly granite and pegmatites. The smoky color is caused by natural irradiation of aluminum impurities within the crystal lattice.
Uses & applications
Used primarily in jewelry as a gemstone, for ornamental carvings, and as a popular collector's mineral. Historically used for making early sunglasses in China.
Geological facts
The national gemstone of Scotland is a variety of smoky quartz known as Cairngorm. Large crystals weighing over 100 pounds are not uncommon in pegmatite deposits.
Field identification & locations
Identify by its translucence, conchoidal (shell-like) fracture, and the fact it can scratch glass but not topaz. Commonly found in mountainous regions like the Alps, Brazil, and the United States (Colorado).
