metamorphic
Polished gray pebble, likely quartzite
Quartzite, composed predominantly of quartz (SiO₂); identification from the image is provisional
AI-generated identification · may be incorrectSmooth, rounded, polished stone with a gray-white groundmass and dark streaks. Quartzite is typically Mohs 7, vitreous to dull, with interlocking quartz grains and no cleavage; specific gravity about 2.6–2.7.
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Physical properties
Smooth, rounded, polished stone with a gray-white groundmass and dark streaks. Quartzite is typically Mohs 7, vitreous to dull, with interlocking quartz grains and no cleavage; specific gravity about 2.6–2.7.
Formation & geological history
Quartz-rich sandstone recrystallized under heat and pressure during metamorphism; such rocks form across many geological ages and mountain belts.
Uses & applications
Small polished specimens are used for collecting and decoration; quartzite is also used as crushed stone, paving, and building material.
Geological facts
The dark bands may be mineral impurities or veining; a photo alone cannot reliably distinguish quartzite from other gray, quartz-rich stones.
Field identification & locations
Look for a hard, quartz-rich texture and grains that resist scratching by a steel knife; common sources include metamorphic belts and river or beach gravels. A definitive identification may require close examination or testing.
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