metamorphic
Quartzite
Metamorphic Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white, occasionally translucent; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 - 2.7
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white, occasionally translucent
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white, occasionally translucent; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 - 2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together, losing the original clastic texture.
Uses & applications
Used heavily in road construction (crushed stone), as railway ballast, for abrasive applications, and as dimension stone in architecture and countertops.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than along the boundaries between them, unlike sandstone which breaks around grains.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass or steel) and sugary, crystalline appearance on fresh surfaces. Common in mountain belts and shield areas.
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