metamorphic
Quartzite
Quartzite (SiO2 principal component)
Hardness: 7 on Mohs scale; Color: typically white, gray, or brown but can be tinted pink or green; Luster: Vitreous to dull; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or brown but can be tinted pink or green; 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 subjected to high heat and pressure, causing quartz grains to recrystallize and fuse together. Can range from Precambrian to Mesozoic in age.
Uses & applications
Used as decorative stone in architecture, as crushed stone for road construction and railway ballast, in the manufacture of glass and ceramics, and as a durable material for kitchen countertops.
Geological facts
Quartzite is so tough that it often survives intense erosion better than the surrounding rocks, frequently forming the caps of ridges and mountains. It is more resistant to weathering than the sandstone it originated from.
Field identification & locations
Identify it by its extreme hardness (it will scratch glass easily) and its sugary, crystalline surface. Unlike marble, it does not fizz when exposed to acid. Commonly found in folded mountain belts globally.
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