metamorphic
Quartzite
Quartzite (chiefly SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white with hints of tan/yellow; Luster: Vitreous to dull; Crystal structure: Granular/Massive; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white with hints of tan/yellow
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white with hints of tan/yellow; Luster: Vitreous to dull; Crystal structure: Granular/Massive; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, causing the original quartz grains to recrystallize and fuse together.
Uses & applications
Used in construction as road ballast, gravel, and dimension stone; also as a source of silica for glass making and metallurgy.
Geological facts
Quartzite is so tough that it often survives intense weathering better than other rocks, frequently capping hills and mountain ridges. It will scratch glass easily, unlike sandstone.
Field identification & locations
Identify by its extreme hardness and grainy, sugary texture. It is found globally in mountainous regions and areas with ancient continental shields.
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