metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: White to grey (sometimes reddish or pink), Luster: Vitreous to dull, Crystal structure: Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: White to grey (sometimes reddish or pink), Luster: Vitreous to dull, Crystal structure: Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together. Can date back to any geological age.
Uses & applications
Used in construction as a decorative stone, road ballast, roofing material, and in the production of glass and silicon due to high silica content.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock in weathering processes, resulting in prominent ridges and mountain peaks. It will scratch glass easily.
Field identification & locations
Identify by its extreme hardness and grainy texture that looks like sandstone but breaks through individual grains rather than around them. Common in mountainous regions globally.
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