metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: white to light gray/tan; Luster: vitreous to dull; Crystal structure: trigonal (microcrystalline); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- white to light gray/tan
- Luster
- vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: white to light gray/tan; Luster: vitreous to dull; Crystal structure: trigonal (microcrystalline); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny).
Uses & applications
Used in construction as road ballast, gravel, and dimension stone; high-purity quartzite is used to produce silica for glass and metal smelting.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, frequently forming the peaks of ridges and mountains.
Field identification & locations
Identify in the field by its extreme hardness (it will scratch glass easily) and its sugary, granular texture. It is found worldwide in metamorphic belts.
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