mineral
Smoky Quartz with Feldspar
SiO2 (Quartz) with KAlSi3O8 (Feldspar)
Hardness: 7 (Quartz), 6 (Feldspar). Color: Dark brown to black, greyish (Smoky Quartz) with white or opaque areas (Feldspar). Luster: Vitreous. Crystal Structure: Hexagonal (Quartz), Monoclinic/Triclinic (Feldspar).
- Hardness
- 7 (Quartz), 6 (Feldspar)
- Luster
- Vitreous
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Physical properties
Hardness: 7 (Quartz), 6 (Feldspar). Color: Dark brown to black, greyish (Smoky Quartz) with white or opaque areas (Feldspar). Luster: Vitreous. Crystal Structure: Hexagonal (Quartz), Monoclinic/Triclinic (Feldspar).
Formation & geological history
Typically forms in igneous rocks like granite and pegmatites. The smoky color in quartz is usually due to natural irradiation of aluminum impurities.
Uses & applications
Often collected by rock hounds. Clearer smoky quartz is used in jewelry, but pieces like this are mostly considered collection specimens.
Geological facts
Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm'.
Field identification & locations
Can be identified by the glassy luster, conchoidal fracture of the quartz, and its characteristic brownish-grey to black color. Rough specimens are common worldwide, especially in granite-rich regions.
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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
Nephrite Jade
Nephrite
Mineral/Rock