metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 (Mohs scale), Color: light gray to white, Luster: vitreous 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: light gray to white, Luster: vitreous to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific gravity: 2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure caused the original quartz sand grains to recrystallize and fuse together. This specimen has been rounded by fluvial or marine water erosion.
Uses & applications
Used as an abrasive, in construction as crushed stone, and sometimes as a decorative landscape material or semi-precious stone for tumbling.
Geological facts
Quartzite is so strong and hard that it typically breaks through the quartz grains rather than along their boundaries, unlike its parent rock, sandstone. It is often more resistant to weathering than the surrounding rock.
Field identification & locations
Identify by its ability to easily scratch glass and its grainy, crystalline texture that looks like sandpaper but feels smooth due to water polishing. Found globally in riverbeds, beaches, and glacial till.
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