metamorphic
Quartzite River Rock
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale), Color: tan to light brown with cloudy translucence, Luster: waxy to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: tan to light brown with cloudy translucence, Luster: waxy to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific gravity: 2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific specimen has been further shaped and smoothed by fluvial (river) erosion over thousands of years.
Uses & applications
Used in landscaping, construction aggregate, aquarium decor, and occasionally as a source of high-purity silica for glassmaking.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock in mountain ranges, becoming the cap rock. In riverbeds, its high hardness allows it to stay intact while softer minerals dissolve or crumble into silt.
Field identification & locations
Identify in the field by its rounded, smooth texture and the fact that it can scratch glass easily. Common in riverbeds, glacial deposits, and mountain wash. Collectors look for unique banding or 'sun bleaching' on surface rinds.
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