metamorphic
Quartzite
Quartzite (predominantly SiO2)
Hardness: 7 (Mohs), Color: White to yellowish-tan, Luster: Vitreous to dull, Crystal structure: Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs), Color: White to yellowish-tan, Luster: Vitreous to dull, Crystal structure: Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed by the metamorphism of quartz-rich sandstone under heat and pressure, typically in orogenic belts. Most are Proterozoic to Paleozoic in age.
Uses & applications
Used in construction for road ballast, floor tiles, and countertop material. Also used as a historical source for stone tools.
Geological facts
Quartzite is so tough that it often forms the ridges of mountain ranges because it resists erosion better than the surrounding rocks. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify by its hardness (7), lack of reaction to acid, and grainy, sugary texture. It is commonly found in mountainous regions or as rounded pebbles in riverbeds and beaches.
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