metamorphic
Quartzite
Quartzite (Silicon dioxide, SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: Brownish, tan, grey, or white depending on impurities, Luster: Vitreous to dull, Crystal structure: Massive (interlocking quartz grains), Cleavage: None, Specific gravity: ~2.6-2.8
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Physical properties
Hardness: 7 (Mohs scale), Color: Brownish, tan, grey, or white depending on impurities, Luster: Vitreous to dull, Crystal structure: Massive (interlocking quartz grains), Cleavage: None, Specific gravity: ~2.6-2.8
Formation & geological history
Formed from the metamorphism of pure or nearly pure quartz sandstone due to heat and pressure. The original quartz sand grains and the cementing material bind together into a tough, solid mass. Found in areas of past or present tectonic collision.
Uses & applications
Used as a decorative stone, for countertops, roofing tiles, as aggregate in construction, and historically for stone tools due to its hardness and conchoidal fracture.
Geological facts
Because it is so tough and resistant to weathering, quartzite often forms ridges and hilltops in mountainous areas. When broken, it typically fractures through the quartz grains rather than around them, which distinguishes it from sandstone.
Field identification & locations
Identified by its hardness (will scratch glass), granular texture (though heavily metamorphosed pieces may look very smooth), and lack of cleavage. Often found as rounded river rocks or cobbles due to its durability.
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