metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, color ranges from white and gray to pink, red, and yellowish due to iron oxide impurities, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, no true cleavage, specific gravity of 2.65 to 2.70.
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Physical properties
Hardness of 7 on the Mohs scale, color ranges from white and gray to pink, red, and yellowish due to iron oxide impurities, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, no true cleavage, specific gravity of 2.65 to 2.70.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high tectonic heat and pressure, typically during mountain-building events over millions of years.
Uses & applications
Used widely in construction as crushed stone for roadbeds, railway ballast, dimension stone for building facings, roofing tiles, and in the manufacture of silica brick and ferrosilicon.
Geological facts
Quartzite is extremely resistant to chemical weathering and erosion, which is why ridges formed of quartzite often persist as high mountain crests or prominent hills.
Field identification & locations
Can be identified in the field by its sugary texture on broken surfaces, extreme hardness that scratches glass easily, and the fact that it breaks through the quartz grains rather than around them like sandstone.
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