metamorphic
Quartzite Pebble (or Milky Quartz Pebble)
Metamorphic Quartzite (SiO2)
AI-generated identification · may be incorrectHardness 7 on the Mohs scale, pale gray to milky white color with subtle iron staining, vitreous to waxy or dull weathered luster, trigonal crystal system (composed of interlocking recrystallized quartz grains), conchoidal to uneven fracture, specific gravity around 2.65.
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Physical properties
Hardness 7 on the Mohs scale, pale gray to milky white color with subtle iron staining, vitreous to waxy or dull weathered luster, trigonal crystal system (composed of interlocking recrystallized quartz grains), conchoidal to uneven fracture, specific gravity around 2.65.
Formation & geological history
Formed when pure quartz sandstone was subjected to intense heat and tectonic pressure, recrystallizing into extremely dense quartzite, then subsequently eroded, shaped, and smoothed by fluvial or coastal wave action into a rounded river pebble.
Uses & applications
Commonly used in crushed stone aggregate, railway ballast, landscaping gravel, and as a refractory material in industrial silicon manufacturing due to high thermal and chemical resistance.
Geological facts
Quartzite is so tough and resilient that it fractures directly through its constituent quartz grains rather than along the cement between them, which distinguishes it from sandstone.
Field identification & locations
Easily identified in the field by its high hardness (scratches glass with ease, cannot be scratched by a steel nail), lack of acid reaction, sugary or granular interlocking texture, and smooth rounded pebble morphology. Found globally along riverbeds, beaches, and glacial gravel deposits.
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