mineral
Smoky Quartz
Silicon Dioxide (SiO2) with natural radiation treatment
Hardness: 7 on Mohs scale; Color: Translucent smoky brown to grey; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (Trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Translucent smoky brown to grey
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 7 on Mohs scale; Color: Translucent smoky brown to grey; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (Trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed in igneous and metamorphic rocks, particularly granite pegmatites. The smoky color is caused by natural gamma radiation from the surrounding rock that activates aluminum impurities within the quartz lattice.
Uses & applications
Used in jewelry, decorative carvings, lapidary arts, and by mineral collectors. In industry, quartz is used for its piezoelectric properties and in glass making.
Geological facts
The smoky color can be reversed by heating the stone to high temperatures, and conversely, clear quartz can be turned smoky through artificial irradiation. It is the national gemstone of Scotland.
Field identification & locations
Identify by its characteristic 'smoky' transparency, hardness (it will scratch glass), and lack of cleavage. Commonly found in Brazil, Madagascar, and the Swiss Alps. For collectors, look for clarity and depth of color.
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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