metamorphic
River Quartzite / Tumble-Polished Quartz
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: Creamy off-white to yellowish-tan, Luster: Vitreous to waxy (when smoothed), Crystal structure: Trigonal/Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Creamy off-white to yellowish-tan, Luster: Vitreous to waxy (when smoothed), Crystal structure: Trigonal/Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure. The specimen shown appears to be water-worn or mechanically tumbled, originating from ancient sedimentary deposits that underwent regional metamorphism.
Uses & applications
Commonly used in construction as crushed stone, in industrial glass making, as architectural accents, and frequently used in rock tumbling hobbies for decorative river stones.
Geological facts
Quartzite is harder than the sandstone it originates from and will actually break across the quartz grains rather than around them. It is one of the most durable and weather-resistant rocks on the Earth's surface.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its grainy, 'sugary' texture on fresh breaks. It is ubiquitous in riverbeds and glacial tilth across North America and Europe.
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