metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: White to grey, often with reddish or yellowish iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7.
- Hardness
- 7 on Mohs scale
- Color
- White to grey, often with reddish or yellowish iron staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White to grey, often with reddish or yellowish iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, creating an extremely hard and durable rock.
Uses & applications
Used widely in construction as road ballast, roofing tiles, and flooring. Highly valued for decorative countertops, wall cladding, and as a source of silica in glass manufacturing.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, forming prominent ridges and hills. It is often confused with marble but can be distinguished by its superior hardness.
Field identification & locations
Identify in the field by its ability to scratch glass and its sugary, crystalline texture on fresh breaks. It is commonly found in ancient mountain belts and cratons globally, such as the Appalachians and the Alps.
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