metamorphic
Blue Quartzite
Silicon Dioxide (SiO2) with inclusions
Hardness: 7 on Mohs scale; Color: Grey-blue to lavender-blue; Luster: Vitreous to dull; Crystal Structure: Trigonal (hexagonal) system of microcrystalline grains; Cleavage: None (conchoidal fracture); Specific Gravity: 2.63 - 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Grey-blue to lavender-blue
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grey-blue to lavender-blue; Luster: Vitreous to dull; Crystal Structure: Trigonal (hexagonal) system of microcrystalline grains; Cleavage: None (conchoidal fracture); Specific Gravity: 2.63 - 2.65.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. Under intense heat and pressure, the quartz grains recrystallize and interlock. The blue coloration is typically caused by inclusions of minerals like dumortierite, crocidolite, or tourmaline.
Uses & applications
Used primarily as decorative stones, in landscaping, as tumbled stones for crystal healing or decor, and occasionally as a gemstone in inexpensive jewelry (cabochons).
Geological facts
Quartzite is so tough that it often outlasts the surrounding softer rocks through millions of years of erosion, creating resistant mountain ridges. The blue variety is particularly prized for its serene aesthetic.
Field identification & locations
Identify in the field by its grainy, sugary texture that resembles sandstone but cannot be scratched by a steel knife. It breaks across grains rather than around them. Found in high concentrations in Brazil, South Africa, and parts of the United States like Virginia and Wisconsin.
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