metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: White to grey, sometimes yellowish; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 - 2.7
- Hardness
- 7 on Mohs scale
- Color
- White to grey, sometimes yellowish
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White to grey, sometimes yellowish; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 - 2.7
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure causes the sand grains to recrystallize and fuse together.
Uses & applications
Used in construction (dimension stone), road ballast, manufacturing of glass, and occasionally as decorative landscaping stone or semi-precious gemstones.
Geological facts
Quartzite is so hard and dense that when struck, it breaks through the quartz grains rather than around them, which is a key distinction from sandstone.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Often found in mountain ranges or Shield areas like the Appalachians or the Canadian Shield.
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