metamorphic
Quartzite
Quartzite (Metamorphic Quartz Sandstone)
Hardness: 7 on the Mohs scale. Color: Brownish-pink, tan, gray, or white. Luster: Vitreous to greasy on fractured surfaces. Crystal structure: Trigonal (microcrystalline intergrown quartz crystals). Cleavage: None (fractures conchoidally). Specific gravity: 2.65 - 2.75.
- Hardness
- 7 on the Mohs scale
- Color
- Brownish-pink, tan, gray, or white
- Luster
- Vitreous to greasy on fractured surfaces
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Physical properties
Hardness: 7 on the Mohs scale. Color: Brownish-pink, tan, gray, or white. Luster: Vitreous to greasy on fractured surfaces. Crystal structure: Trigonal (microcrystalline intergrown quartz crystals). Cleavage: None (fractures conchoidally). Specific gravity: 2.65 - 2.75.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically within tectonic mountain-building belts. Geological age varies widely from Precambrian to Cenozoic.
Uses & applications
Used in construction, as crushed stone for roadbeds, railway ballast, manufacturing of silica bricks, and occasionally as an ornamental stone or for decorative landscaping.
Geological facts
Because quartz is extremely resistant to weathering, quartzite ridges often stand out as prominent, erosion-resistant hills or mountains in the landscape.
Field identification & locations
Can be identified in the field by its inability to be scratched by a steel knife (hardness > 5.5), lack of visible porosity, and the way it breaks across quartz grains rather than around them like sandstone. Found worldwide.
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