metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white with iron staining (yellow/brown/pink); Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white with iron staining (yellow/brown/pink)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white with iron staining (yellow/brown/pink); Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the original quartz grains to recrystallize and fuse together into a dense, hard mass. Commonly found in mountain belts and Precambrian shields.
Uses & applications
Used as a decorative stone in architecture, as crushed stone for road construction, in the manufacturing of glass and ceramics, and as a durable material for countertops and flooring.
Geological facts
Quartzite is so hard that it can scratch steel easily. It is often more resistant to weathering than its surrounding rocks, which is why it often caps mountain peaks and ridges. It is often confused with marble, but marble will react with acid while quartzite will not.
Field identification & locations
Identify in the field by its extreme hardness and its sugary, crystalline texture where broken. It will not fizz with HCl acid. Found abundantly in areas with ancient mountain building history like the Appalachians or the Scottish Highlands.
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