metamorphic
Quartzite
Quartzite (chiefly SiO2)
Hardness: 7 (Mohs scale), Color: White, gray, or tan with reddish tints from iron, Luster: Vitreous to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None, breaks with conchoidal fracture.
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Physical properties
Hardness: 7 (Mohs scale), Color: White, gray, or tan with reddish tints from iron, Luster: Vitreous to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None, breaks with conchoidal fracture.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. Geological age varies by region, often Proterozoic to Paleozoic.
Uses & applications
Used in construction as crushed stone for road ballast, as dimension stone in architecture (countertops, tiles), and in glass manufacturing if high purity.
Geological facts
Quartzite is so tough that it often survives intense erosion better than the surrounding rocks, forming prominent ridges and peaks in mountain ranges.
Field identification & locations
Identify in the field by its ability to scratch glass and its lack of reaction to acid. It is commonly found in metamorphic belts around the world, often occurring as water-worn pebbles in riverbeds or beaches.
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