metamorphic
Quartzite
Quartzite (primarily SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: White to light gray; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65
- Hardness
- 7 on Mohs scale
- Color
- White to light gray
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White to light gray; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular); 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 sand grains to recrystallize and fuse together into a dense, crystalline rock. Often found in Precambrian or Paleozoic formations.
Uses & applications
Used in construction as crushed stone for road gravel and railway ballast, in the glass industry, and for landscaping or decorative stone surfaces.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock, forming resistant ridges or mountaintops. It is harder than steel and can easily scratch a glass plate.
Field identification & locations
Identify in the field by its extreme hardness and granular, sugary appearance. Unlike marble, it will not fizz when exposed to acid. Commonly found in mountainous regions such as the Appalachian or Rocky Mountains.
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