metamorphic
Blue Quartzite
Quartzite with inclusions (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-blue to deep blue; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Grayish-blue to deep blue
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-blue to deep blue; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. The blue color often results from the presence of tiny inclusions of blue minerals like dumortierite or magnesio-riebeckite during high pressure and temperature conditions.
Uses & applications
Used primarily for decorative purposes, landscape stone, construction aggregate, and occasionally in jewelry as cabochons or tumbled stones.
Geological facts
Quartzite is so strong that when it breaks, it fractures through the quartz grains rather than along the boundaries between them, unlike sandstone.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Often found in ancient mountain belts where intense tectonic activity occurred.
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