metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, but can be pink or reddish due to iron oxides; Luster: Vitreous to dull; Crystal structure: Trigonal (hexagonal) system; Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.6 - 2.8.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, but can be pink or reddish due to iron oxides; Luster: Vitreous to dull; Crystal structure: Trigonal (hexagonal) system; Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.6 - 2.8.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under intense heat and pressure, the individual quartz grains recrystallize and fuse together into a dense, crystalline structure.
Uses & applications
Used as a decorative stone in architecture, a ballast for railroads, in glass making (if extremely pure), and as a crushed stone for construction and road building.
Geological facts
Quartzite is so durable that it often remains as ridges or peaks after softer surrounding rocks have eroded away. It is significantly harder than the sandstone from which it originates and will scratch glass easily.
Field identification & locations
Identify in the field by its granular, sugary appearance on fresh surfaces and its ability to scratch glass. It lacks the 'fizz' response to acid that marble (its lookalike) has. Commonly found in folded mountain belts globally.
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