metamorphic
Quartzite
Metamorphic quartz-rich rock
Hardness of 7 on the Mohs scale, typically white, gray, or pinkish in color, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, lacks distinct cleavage, and has a specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, typically white, gray, or pinkish in color, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, lacks distinct cleavage, and has a specific gravity around 2.65.
Formation & geological history
Formed from quartz arenite sandstone subjected to high heat and pressure through regional or contact metamorphism, typically occurring over millions of years in mountain-building belts.
Uses & applications
Used in construction, as crushed stone for roadbeds, in manufacturing railroad ballast, as a decorative building stone, and in the production of silica brick and ferrosilicon.
Geological facts
Because quartz is extremely resistant to weathering, quartzite ridges often form prominent, high-standing mountain crests. Unlike sandstone, quartzite breaks across the quartz grains rather than around them.
Field identification & locations
Can be identified in the field by its hardness (it will easily scratch glass and cannot be scratched by a steel knife) and the sugary texture of fractured surfaces where quartz crystals break.
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