metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, brown, or grayish-white; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, or grayish-white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, brown, or grayish-white; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events. The original quartz grains recrystallize into a locked mosaic.
Uses & applications
Used in construction as crushed stone or road ballast, as a flux in metallurgy, in glassware, and occasionally as decorative landscaping stone.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks, forming distinctive ridges and jagged mountain peaks. It will scratch glass easily, unlike similar-looking sandstone.
Field identification & locations
Identify in the field by its grainy, sugary texture and extreme hardness. It won't effervesce with acid. Commonly found in metamorphic belts throughout the Appalachian Mountains and the Great Lakes region.
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