metamorphic
Quartzite River Rock
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: Grayish-green to white with brownish oxidation and dark inclusions, Luster: Dull to waxy when water-worn, Structure: Granular/Fine-grained, Cleavage: None
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Physical properties
Hardness: 7 (Mohs scale), Color: Grayish-green to white with brownish oxidation and dark inclusions, Luster: Dull to waxy when water-worn, Structure: Granular/Fine-grained, Cleavage: None
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, often during mountain-building events. This specific specimen has been further smoothed by river or coastal erosion.
Uses & applications
Commonly used in landscaping, as aggregate in construction, or for decorative purposes in rock gardens. Polished versions are used in crafts.
Geological facts
Quartzite is so tough that it often survives billions of years of erosion where other rocks have crumbled. It breaks through the grains of the original sand rather than around them, unlike sandstone.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its grainy, crystalline appearance beneath a smooth surface. Commonly found in riverbeds and mountainous glacial deposits.
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