metamorphic
Quartzite
Metamorphic Quartz Sandstone (SiO2)
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, red, and purple due to iron impurities, vitreous to greasy luster, massive to granular crystal structure, lacks prominent cleavage, specific gravity of 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 purple due to iron impurities, vitreous to greasy luster, massive to granular crystal structure, lacks prominent cleavage, specific gravity of 2.65.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high temperatures and pressures usually associated with tectonic compression during mountain building events (orogenesis).
Uses & applications
Used in construction, railroad ballast, crushed stone for road aggregates, decorative landscaping, and occasionally for monumental masonry or countertops.
Geological facts
Because quartz is extremely resistant to weathering, quartzite ridges often form prominent, rugged mountain peaks and ridges resistant to erosion.
Field identification & locations
Can be identified in the field by its extreme hardness (scratches glass easily, cannot be scratched by a knife) and the fact that it breaks across the quartz grains rather than around them like sandstone. Found worldwide globally in mountainous regions and ancient cratons.
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