metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs), Color: Grey, brown, and tan (stained by iron oxides), Luster: Vitreous to dull, Crystal structure: Trigonal/Hexagonal (granular texture), Cleavage: None, Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs), Color: Grey, brown, and tan (stained by iron oxides), Luster: Vitreous to dull, Crystal structure: Trigonal/Hexagonal (granular texture), Cleavage: None, Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny).
Uses & applications
Used as crushed stone in construction, road ballast, and decorative landscaping. High-quality slabs are used for kitchen countertops and floor tiles.
Geological facts
Quartzite is so tough that it often survives erosion better than any other rock, frequently forming the tops of ridges and mountains.
Field identification & locations
Identify by its extreme hardness (it will scratch glass) and its sugary, crystalline texture where broken. Commonly found in metamorphic belts globally, such as the Appalachian or Rocky Mountains.
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