metamorphic
Rounded gray pebble, likely quartz-rich metamorphic rock
Probable quartzite or fine-grained gneiss; mainly SiO₂ quartz with possible feldspar and mica
AI-generated identification · may be incorrectGray, smooth, water-worn surface with subtle sparkling grains and no obvious cleavage; quartz hardness is about 7 Mohs, with a glassy to dull luster. Exact identification is limited by the small, weathered specimen and image quality.
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Physical properties
Gray, smooth, water-worn surface with subtle sparkling grains and no obvious cleavage; quartz hardness is about 7 Mohs, with a glassy to dull luster. Exact identification is limited by the small, weathered specimen and image quality.
Formation & geological history
Likely formed by metamorphism of quartz-rich sandstone (quartzite) or an original crystalline rock, then rounded by stream or coastal transport. The metamorphic age cannot be determined visually.
Uses & applications
Quartzite is used as aggregate, building stone, paving, and sometimes decorative material; attractive polished pieces may be collected but are generally low value.
Geological facts
A steel knife should not easily scratch quartz-rich material, while quartzite commonly breaks across grains rather than along flat cleavage surfaces.
Field identification & locations
Common in gravel beds, river channels, beaches, and glacial deposits worldwide; test hardness, streak, grain texture, and acid reaction, and inspect a fresh break for interlocking quartz grains.
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