metamorphic
White quartzite pebble
Quartzite, composed predominantly of quartz (SiO₂)
AI-generated identification · may be incorrectTypically Mohs hardness 7, white to pale gray, with a dull to sugary or vitreous luster; massive and nonfoliated, with no obvious cleavage. The rounded shape indicates natural water or abrasion, though the surface may be polished or weathered.
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Physical properties
Typically Mohs hardness 7, white to pale gray, with a dull to sugary or vitreous luster; massive and nonfoliated, with no obvious cleavage. The rounded shape indicates natural water or abrasion, though the surface may be polished or weathered.
Formation & geological history
Forms when quartz-rich sandstone is recrystallized under heat and pressure, commonly during mountain-building; its exact geological age cannot be determined from the image. Resistant fragments accumulate in riverbeds, beaches, and glacial deposits.
Uses & applications
Used as durable aggregate, paving and decorative stone; attractive white pieces are sold as landscaping or craft stones, but this specimen is unlikely to be gem-grade.
Geological facts
Quartzite is harder and generally more tightly crystalline than its sandstone precursor. A useful test is that quartzite scratches ordinary glass, whereas a steel blade usually does not scratch it.
Field identification & locations
Common in metamorphic belts and derived gravels worldwide, including the Appalachians, Rocky Mountains, Alps, India, Brazil, and Scandinavia. Look for interlocking quartz grains and a lack of visible sand-layering; acid produces no reaction.
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