metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, red, and brown depending on impurities, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, indistinct cleavage, and specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, red, and brown depending on impurities, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, indistinct cleavage, and specific gravity around 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under intense heat and tectonic pressure, typically during mountain-building events over millions of years.
Uses & applications
Used extensively in construction as crushed stone for road bases, dimension stone for building facades, roofing tiles, and sometimes in landscaping or decorative countertops.
Geological facts
Because quartz is extremely resistant to weathering, quartzite ridges often stand out as prominent hills or mountain ranges in worn-down ancient mountain belts like the Appalachian Mountains.
Field identification & locations
Identified in the field by its hardness (will easily scratch glass and cannot be scratched by a steel knife) and the sugary texture of interlocking quartz crystals visible on broken surfaces. Found globally wherever ancient sandstones have undergone regional metamorphism.
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