metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white with pinkish or dark inclusions; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular texture); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white with pinkish or dark inclusions
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white with pinkish or dark inclusions; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular texture); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone. Intense heat and pressure cause the quartz grains to recrystallize and fuse together, creating a hard, dense rock. This specimen appears water-worn or weathered.
Uses & applications
Used as decorative stone, crushed stone for road construction, railway ballast, and in the manufacturing of glass and ceramics. High-quality pieces are used for countertops and floor tiles.
Geological facts
Quartzite is so hard that it will scratch glass and even steel. Unlike sandstone, which breaks around its grains, quartzite breaks through its grains due to the complete recrystallization of the silica.
Field identification & locations
Identify by its extreme hardness and granular, sugary appearance. It is commonly found in mountain ranges and areas with ancient continental crust. Collectors find it in riverbeds as rounded cobbles like this one.
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