metamorphic
Blue Quartzite
Metamorphic Quartzite (SiO2)
Hardness: 7 on the Mohs scale; Color: Blue to bluish-gray; Luster: Vitreous to greasy; Crystal structure: Trigonal (microcrystalline quartz grains fused together); Cleavage: None, fractures conchoidally; Specific gravity: 2.65.
- Hardness
- 7 on the Mohs scale
- Color
- Blue to bluish-gray
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on the Mohs scale; Color: Blue to bluish-gray; Luster: Vitreous to greasy; Crystal structure: Trigonal (microcrystalline quartz grains fused together); Cleavage: None, fractures conchoidally; Specific gravity: 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert that has undergone high temperatures and pressures during regional metamorphism. Geological age varies widely depending on the formation site, ranging from Precambrian to Cenozoic.
Uses & applications
Used primarily as decorative stone, in landscaping, architectural facing, and sometimes cut into cabochons for jewelry.
Geological facts
The distinctive blue color in quartzite is often due to microscopic inclusions of dumortierite, crocidolite, or lazulite within the quartz matrix.
Field identification & locations
Can be identified in the field by its hardness (scratches glass easily), inability to be split along bedding planes (unlike sandstone), and its resistance to weathering. Found worldwide in mountainous metamorphic belts.
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