metamorphic
Quartzite
Quartzite (composed primarily of Silica, SiO2)
Hardness: 7 on Mohs scale; Color: Pink, reddish, or white; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Pink, reddish, or white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Pink, reddish, or white; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during tectonic plate convergence (mountain building).
Uses & applications
Used in construction as crushed stone or decorative facing, in the glass industry as a source of silica, and as a durable material for countertops and flooring.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the tops of ridges and hills because it resists weathering better than surrounding rocks. It can be distinguished from sandstone because it fractures through the quartz grains rather than around them.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and granular, 'sugary' appearance. It is commonly found in older mountain ranges and shields globally.
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