metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often with shades of green or pink; Luster: vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: none, breaks with conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Color
- typically white to gray, often with shades of green or pink
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, often with shades of green or pink; Luster: vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: none, breaks with conchoidal fracture.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under high heat and pressure, the original quartz grains recrystallize and fuse together into a dense, hard mass.
Uses & applications
Used in construction as road ballast, gravel, or flooring. Crushed quartzite is used in the manufacture of glass and silicon. High-purity specimens are used as decorative stones or in jewelry.
Geological facts
Quartzite is so hard that it can scratch steel and glass easily. In many mountain ranges, quartzite forms the highest peaks because it is extremely resistant to chemical and physical weathering.
Field identification & locations
Identified in the field by its hardness (it will scratch glass), its grainy sandpaper-like texture (though smoother than sandstone), and its lack of reaction to acid. Often found in metamorphic belts and mountain ranges.
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