metamorphic
River Pebble (Quartzite)
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: Creamy white with tan/grey inclusions, Luster: Vitreous to waxy (especially when wet), Crystal structure: Hexagonal (microcrystalline), Cleavage: None/Conchoidal fracture
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Physical properties
Hardness: 7 (Mohs scale), Color: Creamy white with tan/grey inclusions, Luster: Vitreous to waxy (especially when wet), Crystal structure: Hexagonal (microcrystalline), Cleavage: None/Conchoidal fracture
Formation & geological history
Formed from the recrystallization of quartz sandstone through heat and pressure (metamorphism), then rounded over time by water erosion in riverbeds.
Uses & applications
Used in landscaping, construction aggregate, aquarium decor, and as a common find for beginning rock hunters.
Geological facts
Quartzite is harder than the steel of a pocket knife. While it started as sedimentary sand, the metamorphism makes it one of the most durable rocks on Earth's surface.
Field identification & locations
Identify by its hardness (cannot be scratched by steel) and lack of reaction to acid. Commonly found in riverbeds, glacial deposits, and beaches.
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