metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: tan, yellowish, and grey with dark inclusions, Luster: Vitreous to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, yellowish, and grey with dark inclusions, Luster: Vitreous to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure reciprocal to tectonic activity fuse quartz grains together into a dense, crystalline rock.
Uses & applications
Crushed stone for road construction, railway ballast, and occasionally used as decorative landscaping stone or tumbled for hobbyist collections.
Geological facts
Quartzite is so tough that it often survives erosion better than the surrounding rocks, which is why it is frequently found as rounded pebbles in riverbeds or beach deposits long after the parent rock has weathered away.
Field identification & locations
Identify by its ability to scratch glass and its grainy, sandpaper-like texture that unlike sandstone, breaks through the grains rather than around them. Commonly found in riverbeds and glacial tills.
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