metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or pinkish due to iron oxide; Luster: vitreous to dull; Crystal structure: trigonal (hexagonal) system; Cleavage: indistinct; Specific gravity: 2.6-2.65
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or pinkish due to iron oxide
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or pinkish due to iron oxide; Luster: vitreous to dull; Crystal structure: trigonal (hexagonal) system; Cleavage: indistinct; Specific gravity: 2.6-2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. Geological age varies globally based on local tectonic history.
Uses & applications
Used widely in construction as crushed stone for road gravel and railway ballast, as a decorative stone in countertops and wall tiles, and in glass manufacturing.
Geological facts
Quartzite is so durable that it often remains as caps on mountain peaks after surrounding softer rocks have eroded away; it is significantly harder and more resistant than the sandstone from which it originated.
Field identification & locations
Identify in the field by its grainy, sandpaper-like surface that will scratch glass and lacks the reaction to acid seen in marble. It is extremely common in metamorphic belts and glaciated riverbeds.
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