metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: Pinkish-red to tan, 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: Pinkish-red to tan, Luster: Vitreous to dull, Crystal Structure: Hexagonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure. This specimen shows water-worn rounding, suggesting it was found in a riverbed or coastal environment.
Uses & applications
Used in construction as road ballast, railway ballast, and dimension stone; also an industrial source of silica for glass and metal smelting.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges and peaks of mountain ranges because it weathers more slowly than surrounding rocks.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and lack of visible grains compared to sandstone. Often found in glaciated regions or ancient mountain belts.
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