metamorphic
Quartzite
Quartzite (Metamorphic Quartz Sandstone)
Hardness: 7 on Mohs scale. Color: Typically white to gray, but can be pink, purple, or reddish due to iron impurities. Luster: Vitreous to greasy on fresh surfaces. Crystal structure: Interlocking mosaic of quartz crystals. Cleavage: None, breaks with a conchoidal fracture. Specific gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to greasy on fresh surfaces
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Physical properties
Hardness: 7 on Mohs scale. Color: Typically white to gray, but can be pink, purple, or reddish due to iron impurities. Luster: Vitreous to greasy on fresh surfaces. Crystal structure: Interlocking mosaic of quartz crystals. Cleavage: None, breaks with a conchoidal fracture. Specific gravity: 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high heat and pressure, typically in mountain-building belts. Geological age spans across all geological eons, from Precambrian to Cenozoic.
Uses & applications
Used in construction as crushed stone for roadbeds, railway ballast, building stone, and for manufacturing ferrosilicon, silica bricks, and tiles.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering. When sandstone becomes quartzite, the individual sand grains recrystallize and the original pore spaces are destroyed, making it harder than the parent rock.
Field identification & locations
Can be identified in the field by its extreme hardness (scratches glass easily), inability to be split along bedding planes like sandstone, and the sugary texture of interlocking quartz crystals visible on broken surfaces. Found worldwide.
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