metamorphic
Quartzite
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 (Mohs scale), Color: Dirty white to light grey with graininess, Luster: Vitreous to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Dirty white to light grey with graininess, Luster: Vitreous to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.7
Formation & geological history
Formed through the intense heating and pressure (metamorphism) of quartz-rich sandstone. Most commonly found in orogenic (mountain-building) belts where tectonic plates collide.
Uses & applications
Used in construction as crushed stone or road ballast, as a raw material for glass and ceramics (if high purity), and sometimes as dimension stone for buildings.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the resistant ridges and peaks of mountain ranges. It is harder than the steel of a knife blade.
Field identification & locations
Identify in the field by its sugary texture on broken surfaces and its ability to scratch glass easily. It will not react with acid, unlike similar-looking marble.
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