metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, yellow, or brown due to iron oxide impurities. It has a vitreous to greasy luster, a non-foliated massive crystal structure, conchoidal fracture, and lacks distinct cleavage. Specific gravity is approximately 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, yellow, or brown due to iron oxide impurities. It has a vitreous to greasy luster, a non-foliated massive crystal structure, conchoidal fracture, and lacks distinct cleavage. Specific gravity is approximately 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high temperatures and pressures, typically in mountain-building belts (orogens) over millions of years.
Uses & applications
Used in construction, as crushed stone for roadbeds, in the manufacturing of refractory bricks, silica brick, and occasionally as a decorative building stone or for countertops.
Geological facts
Because quartz is extremely resistant to weathering, quartzite ridges often form prominent, rugged mountain ridges and hills that resist erosion better than surrounding rocks.
Field identification & locations
Can be identified in the field by its hardness (it will easily scratch glass and cannot be scratched by a knife blade) and the way it breaks across the quartz grains rather than around them, unlike sandstone.
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