metamorphic
Quartzite River Rock
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: White to grey with tan/brown staining, Luster: Vitreous when wet or polished, dull when dry, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.63-2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: White to grey with tan/brown staining, Luster: Vitreous when wet or polished, dull when dry, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.63-2.65
Formation & geological history
Originates from quartz-rich sandstone that has undergone high heat and pressure (metamorphism), which fuses the quartz grains together into a dense, hard rock. Often found as rounded cobbles due to river transport.
Uses & applications
Used primarily as decorative landscaping stone, in road construction, as railroad ballast, and occasionally for high-durability kitchen countertops.
Geological facts
Quartzite is so hard that it will scratch glass and even high-quality steel. It is one of the most chemically resistant and physically durable rocks on Earth's surface.
Field identification & locations
Identify in the field by its grainy texture that looks like sandstone but won't rub off, and its extreme hardness. Found globally in riverbeds and mountainous regions. Collectors look for unique banding or translucency.
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