metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: Grayish-white to light brown/pink, Luster: Vitreous to dull, Crystal Structure: Trigonal (granular texture), Specific Gravity: 2.6-2.7.
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Physical properties
Hardness: 7 (Mohs scale), Color: Grayish-white to light brown/pink, Luster: Vitreous to dull, Crystal Structure: Trigonal (granular texture), Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the regional or contact metamorphism of quartz sandstone under high heat and pressure, causing quartz grains to recrystallize and fuse.
Uses & applications
Used in construction for road ballast, railway beds, and decorative stone. Sometimes used as a source of silica for glass manufacturing.
Geological facts
Quartzite is one of the most durable and weather-resistant rocks on Earth. Unlike sandstone which breaks around grains, quartzite breaks through the quartz grains.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Look for a sugary, crystalline texture. Found globally in mountainous regions.
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