metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: White, gray, or tan with yellowish iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- White, gray, or tan with yellowish iron staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White, gray, or tan with yellowish iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); specific gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, causing sand grains to recrystallize and fuse together. Often found in orogenic belts.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a raw material in the glass and ceramic industries. Harder specimens are used for decorative landscaping.
Geological facts
Quartzite is so tough that it often survives erosion better than other rocks, frequently capping hills and mountain ridges. It will scratch glass easily, unlike similar-looking limestone.
Field identification & locations
Identify in the field by its sugary texture and extreme hardness. It breaks through the original sand grains rather than around them. Found globally in ancient mountain ranges.
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