metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, color ranges from white and grey to pink, orange, and yellow due to iron oxide impurities, vitreous to greasy luster, non-foliated crystal structure, lacks cleavage, and has a specific gravity of around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, color ranges from white and grey to pink, orange, and yellow due to iron oxide impurities, vitreous to greasy luster, non-foliated crystal structure, lacks cleavage, and has a specific gravity of around 2.65.
Formation & geological history
Formed when quartz-rich sandstone or chert is subjected to high heat and pressure, typically through tectonic compression in orogenic belts. This process recrystallizes the quartz grains into an interlocking mosaic.
Uses & applications
Used widely in construction for crushed stone, railroad ballast, decorative aggregates, and as dimension stone for countertops, wall tiles, and flooring.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why ridges made of quartzite often form prominent mountain ranges or hills as the surrounding softer rocks erode away.
Field identification & locations
Can be identified in the field by its hardness (will easily scratch glass and cannot be scratched by a steel knife) and the way it breaks across the quartz grains rather than around them, unlike sandstone. Found worldwide in ancient mountain belts.
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