metamorphic
Quartzite (River Pebble)
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 (Mohs scale), Color: tan to reddish-brown (likely due to iron oxide staining), Luster: dull to vitreous, Crystal structure: granular/microcrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: tan to reddish-brown (likely due to iron oxide staining), Luster: dull to vitreous, Crystal structure: granular/microcrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific specimen has been rounded and smoothed by water transport in a fluvial (river) environment.
Uses & applications
Used in construction as road ballast or aggregate, as landscaping stone (river rock), and occasionally for decorative lapidary work if highly colored.
Geological facts
Quartzite is so tough that it often outlasts the original bedrock from which it was formed. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a knife) and its grainy, 'sugary' texture visible under a loupe. Commonly found in riverbeds and glacial deposits.
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