metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, typically white to gray or pinkish in color, vitreous to greasy luster, non-foliated massive crystal structure, conchoidal fracture with no true cleavage, specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, typically white to gray or pinkish in color, vitreous to greasy luster, non-foliated massive crystal structure, conchoidal fracture with no true cleavage, specific gravity 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. Geological age can range from Precambrian to Cenozoic.
Uses & applications
Used in construction, as crushed stone for roadbeds, railway ballast, dimension stone, manufacturing of silica brick, and occasionally for decorative landscaping or countertops.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why ridges formed by quartzite layers often remain as prominent hills or mountain crests after surrounding softer rocks have eroded away.
Field identification & locations
Identified in the field by its hardness (will easily scratch glass and cannot be scratched by a steel knife) and the fact that it breaks across the quartz grains rather than around them. Found globally, especially in mountain ranges and ancient cratons.
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