mineral
Quartz (Milky or Smoky variety)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: Clear to white or smoky brown; Luster: Vitreous to greasy; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Clear to white or smoky brown
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on Mohs scale; Color: Clear to white or smoky brown; Luster: Vitreous to greasy; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Quartz forms in a wide variety of environments, most commonly from the cooling of magma (igneous) or precipitation from hydrothermal veins. It is found in rocks ranging from the Archean era to the present day.
Uses & applications
Used extensively in glassmaking, electronics (piezoelectric properties), abrasives, construction as an aggregate, and as semi-precious gemstones in jewelry.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. It is highly resistant to both chemical and physical weathering. Pure quartz is known as rock crystal.
Field identification & locations
Identify in the field by its hardness (it can scratch glass and steel), lack of cleavage, and characteristic glassy luster. Commonly found in granite outcroppings or as loose pebbles in stream beds.
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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