metamorphic
Quartzite
Quartzite (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: tan, grey, buff, or reddish-brown due to iron impurities, Luster: vitreous to dull, Crystal structure: hexagonal (microcrystalline), Cleavage: none, Specific gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, grey, buff, or reddish-brown due to iron impurities, Luster: vitreous to dull, Crystal structure: hexagonal (microcrystalline), Cleavage: none, Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during tectonic plate collisions and mountain-building events.
Uses & applications
Used extensively in construction as road ballast, gravel, and dimension stone for cladding or flooring. High-purity quartzite is used to produce glass and industrial silica.
Geological facts
Quartzite is so tough that it often outlasts other rocks; it can be found capping mountain peaks because it is highly resistant to chemical and physical weathering.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and the way it fractures across individual sand grains rather than around them. Common in Precambrian shields and fold-thrust mountain belts.
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