mineral
Smoky Quartz
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: Smoky brown to black/grey, Luster: Vitreous (glassy), Crystal system: Hexagonal (trigonal), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Smoky brown to black/grey, Luster: Vitreous (glassy), Crystal system: Hexagonal (trigonal), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed in igneous and metamorphic rocks, particularly pegmatites. The smoky color results from natural irradiation of aluminum-bearing quartz over long geological periods.
Uses & applications
Used in jewelry, decorative carvings, and as a popular specimen for mineral collectors. Historically used for one of the first types of sunglasses in China.
Geological facts
The dark color is caused by free silicon formed from silicon dioxide by natural irradiation. Cairngorm is a famous variety of smoky quartz found in the Cairngorm Mountains of Scotland.
Field identification & locations
Identify in the field by its smoky transparency, hardness (it can scratch glass), and lack of cleavage. Commonly found in granitic pegmatites in locations like Brazil, USA (Colorado), and Switzerland.
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Nephrite Jade
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Mineral/Rock
Banded Gneiss (River Rock/Pebble)
Gneiss (specifically a banded variety often found as a river rock)
Metamorphic Rock
![Biotite Schist (Biotite-rich Schist [K(Mg,Fe)3AlSi3O10(F,OH)2]) — metamorphic](https://media.rock.id/9ca564b5-bc87-402b-965a-69b21f9aa6bf-thumbnail.jpg)
Biotite Schist
Biotite-rich Schist [K(Mg,Fe)3AlSi3O10(F,OH)2]
metamorphic