metamorphic
Quartz-rich metamorphic pebble, probably quartzite
Quartzite; predominantly microcrystalline quartz (SiO₂), possibly with feldspar or mica impurities
AI-generated identification · may be incorrectHardness about 7 Mohs; pale tan-gray, granular and massive, with a dull to weakly vitreous luster and no obvious cleavage. The rough, sugary texture and apparent resistance to weathering fit quartzite, though the image alone cannot confirm it over quartz-rich sandstone.
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Physical properties
Hardness about 7 Mohs; pale tan-gray, granular and massive, with a dull to weakly vitreous luster and no obvious cleavage. The rough, sugary texture and apparent resistance to weathering fit quartzite, though the image alone cannot confirm it over quartz-rich sandstone.
Formation & geological history
Quartzite forms when quartz sandstone is recrystallized under heat and pressure, commonly during regional mountain-building; individual grains may be Precambrian to much younger depending on source terrain. This rounded specimen was later transported and polished naturally in a gravel bed or beach.
Uses & applications
Used as crushed aggregate, road stone, riprap, and occasionally dimension stone; attractive pieces are collected but are rarely valuable as gemstones.
Geological facts
Quartzite commonly breaks across grains rather than around them, producing irregular fractures. Its high quartz content makes it resistant to erosion and often concentrates in stream gravels.
Field identification & locations
Found widely in mountain-derived river and beach gravels. Test with a steel knife or glass: genuine quartzite should resist scratching glass and typically leaves a pale streak; inspect a fresh break for fused quartz grains.
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