metamorphic
Quartzite
Metamorphosed Sandstone (SiO2)
Hardness: 7 (Mohs scale); Color: Pinkish-tan or peach/buff; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Pinkish-tan or peach/buff
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Pinkish-tan or peach/buff; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together. The pink/peach hue typically comes from iron oxide impurities.
Uses & applications
Used in construction as road ballast, gravel, and dimension stone. High-purity quartzite is used to produce silica sand for glassmaking and industrial abrasives.
Geological facts
Quartzite is so tough that it often breaks through the individual quartz grains rather than around them, making it more durable than its parent sandstone.
Field identification & locations
Identify by its ability to scratch glass and its sugary, crystalline texture on fresh breaks. Frequently found in mountain ranges and glaciated terrain as rounded cobbles.
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