metamorphic
Brown river pebble, likely quartzite
Quartzite (mostly microcrystalline SiO₂)
AI-generated identification · may be incorrectHardness about 7 Mohs; brown, reddish-brown, and gray banding; dull to subtly silky luster; compact, nonfoliated texture with no obvious cleavage. The rounded shape indicates water abrasion, and the surface appears naturally weathered or lightly smoothed.
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Physical properties
Hardness about 7 Mohs; brown, reddish-brown, and gray banding; dull to subtly silky luster; compact, nonfoliated texture with no obvious cleavage. The rounded shape indicates water abrasion, and the surface appears naturally weathered or lightly smoothed.
Formation & geological history
Likely metamorphosed quartz-rich sandstone, recrystallized under heat and pressure during mountain-building; its exact geological age cannot be determined from the image. Later erosion transported it into a river or gravel deposit.
Uses & applications
Used as durable aggregate, paving stone, landscaping material, and occasionally as a decorative or lapidary specimen. Ordinary pebbles have little commercial value.
Geological facts
Quartzite is typically harder and more resistant to weathering than its sandstone precursor. Brown coloration commonly comes from iron oxides, while the pale line may reflect compositional layering or a weathering vein.
Field identification & locations
Common in river gravels and glacial deposits worldwide, especially near quartzite-bearing mountain belts. A steel file should not scratch it; a streak test, close inspection for fused quartz grains, and acid testing can help distinguish it from sandstone or iron-rich metamorphic rocks.
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