mineral
Smoky Quartz
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: Brownish grey to black, 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: 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).
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Other mineral specimens
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Sandstone with Mineral Veining or Crust
Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)
sedimentary
Schist
Schist
Metamorphic
Potassium Feldspar (Orthoclase)
Orthoclase (KAlSi3O8)
mineral
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic