metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: White, gray, or tan with darker mineral inclusions; Luster: Vitreous to dull; Crystal Structure: Trigonal (granular texture); Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- White, gray, or tan with darker mineral inclusions
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: White, gray, or tan with darker mineral inclusions; Luster: Vitreous to dull; Crystal Structure: Trigonal (granular texture); Cleavage: None; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz sandstone. High pressure and heat cause the quartz grains to recrystallize and fuse together. Often millions to billions of years old.
Uses & applications
Used in construction as road ballast, railway ballast, and building stone. Highly crushed quartzite is used in glass making and industrial abrasives.
Geological facts
Quartzite is so tough that it often survives erosion better than any other rock, frequently forming the tops of hills and ridges. It won't react with acid, unlike its look-alike, marble.
Field identification & locations
Identified in the field by its sugary texture and extreme hardness (it will easily scratch glass). Common in mountainous regions and glacial deposits. Look for a conchoidal fracture pattern.
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