metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, typically white to gray in color, vitreous to greasy luster, non-foliated crystal structure with interlocking quartz grains, conchoidal fracture, specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, typically white to gray in color, vitreous to greasy luster, non-foliated crystal structure with interlocking quartz grains, conchoidal fracture, specific gravity around 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high temperature and tectonic pressure, commonly dating from various geological eras spanning millions of years.
Uses & applications
Used in construction, as crushed stone for road bases, in manufacturing railway ballast, for dimension stone, and occasionally as decorative stone or in countertops.
Geological facts
Because quartz is extremely resistant to weathering, quartzite ridges often form prominent hills or resistant mountain crests, as the original sandstone grains recrystallize tightly together.
Field identification & locations
Can be identified in the field by its inability to be scratched by a knife (hardness > 5.5), lack of fizzing with acid, and the visible fused quartz grains breaking across the grains rather than around them.
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