mineral
Quartz (Smoky Quartz variant)
Silicon Dioxide (SiO2)
Hardness: 7 Mohs; Color: Brown to grayish-black; Luster: Vitreous; Crystal system: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 7 Mohs
- Color
- Brown to grayish-black
- Luster
- Vitreous
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Physical properties
Hardness: 7 Mohs; Color: Brown to grayish-black; Luster: Vitreous; Crystal system: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
Formation & geological history
Formed in igneous and metamorphic rocks, specifically pegmatites and hydrothermal veins. The smoky color is caused by natural irradiation of aluminum-bearing quartz.
Uses & applications
Used in jewelry, decorative ornaments, electronics (piezoelectric properties), and as architectural stone.
Geological facts
The brown color in smoky quartz is often the result of free silicon formed from silicon dioxide by natural radiation. It is the national gem of Scotland, where it is known as Cairngorm.
Field identification & locations
Identified by its smoky transparency, lack of cleavage, and ability to scratch glass. Widely distributed globally, notably in the Swiss Alps, Brazil, and the USA.
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Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Schist
Schist
Metamorphic
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock
Granite
Granite (Phaneritic intrusive igneous rock)
igneous