metamorphic
Quartzite
Quartzite (composed primarily of Silica, SiO2)
Hardness: 7 on Mohs scale; Color: White to light gray; Luster: Vitreous to dull; Crystal structure: Trigonal (as quartz grains); Cleavage: None; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- White to light gray
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White to light gray; Luster: Vitreous to dull; Crystal structure: Trigonal (as quartz grains); Cleavage: None; Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone, where high heat and pressure fuse quartz grains together into a dense, crystalline rock.
Uses & applications
Used extensively in road construction (railway ballast), building stone for countertops and flooring, and as a source of silica in glass manufacturing.
Geological facts
Quartzite is harder and more durable than the sandstone it originates from. It is so tough that it often forms the caprock of mountain ridges because it resists erosion better than surrounding rocks.
Field identification & locations
Identify in the field by its sugary texture and extreme hardness (it will easily scratch glass). Common in mountain ranges and metamorphic belts globally.
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