mineral
Clear Quartz / Rock Crystal
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: Colorless/Transparent; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (Trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Colorless/Transparent
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 7 on Mohs scale; Color: Colorless/Transparent; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (Trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.
Formation & geological history
Formed in igneous, metamorphic, and sedimentary environments. Most clear crystals crystallize from hydrothermal veins or pegmatites as cooling fluids deposit silica.
Uses & applications
Used in jewelry, precision watches, electronics (piezoelectric properties), glassmaking, and as a popular collector's specimen.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. Pure clear quartz is known as 'Rock Crystal' and was historically used for crystal balls.
Field identification & locations
Identified in the field by its hardness (will scratch glass), lack of cleavage, and hexagonal crystal habit when intact. Found globally, with famous deposits in Brazil and Arkansas, USA.
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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
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Nephrite Jade
Nephrite
Mineral/Rock