metamorphic
Quartzite (River Stone)
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: Creamy white to light tan, Luster: Vitreous to waxy, Crystal structure: Trigonal/Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Creamy white to light tan, Luster: Vitreous to waxy, Crystal structure: Trigonal/Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure. The specimen shown is a water-worn river pebble, shaped by fluvial erosion over thousands of years.
Uses & applications
Used in construction as road ballast, in glass manufacturing, and as decorative landscaping stones or aquarium gravel.
Geological facts
Quartzite is one of the most durable rocks on Earth's surface. It can be harder than steel and is often used to make 'stone' tools in prehistoric times because of its sharp edges when broken.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Commonly found in river beds, mountainous regions, or ancient glacial deposits.
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