metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: tan to light brown with white frosting, Luster: vitreous to waxy, Crystal structure: Trigonal (granular), Cleavage: none (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: tan to light brown with white frosting, Luster: vitreous to waxy, Crystal structure: Trigonal (granular), Cleavage: none (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under high pressure and temperature. Primarily from the Proterozoic or Paleozoic eras, found in mountain belts and river beds.
Uses & applications
Used in construction for road ballast and roofing tiles. Higher purity specimens are used in glass manufacturing and as decorative landscaping stones.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than along their boundaries, unlike sandstone. It is one of the most durable materials on Earth's surface.
Field identification & locations
Identify by its ability to scratch glass and its grainy, sugary texture. It is commonly found in beach wash or river gravels. Collectors look for unique colors or surface patterns.
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