sedimentary
Pebble
Lithic fragment / Water-worn rock
Hardness varies greatly depending on composition (typically Mohs 6-7 if quartz-rich), grey-brown color, dull luster, amorphous crystal structure due to weathering and rounding, no distinct cleavage, specific gravity around 2.65.
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Physical properties
Hardness varies greatly depending on composition (typically Mohs 6-7 if quartz-rich), grey-brown color, dull luster, amorphous crystal structure due to weathering and rounding, no distinct cleavage, specific gravity around 2.65.
Formation & geological history
Formed through the mechanical weathering, erosion, and transport of larger parent rocks by water or wind, typically in riverbeds, beaches, or glacial environments over thousands to millions of years.
Uses & applications
Used in landscaping, construction aggregate, decorative pathways, and as raw material for various industrial applications.
Geological facts
Pebbles are classified by their grain size on the Udden-Wentworth scale, specifically ranging from 4 to 64 millimeters in diameter. Water-worn pebbles are classic indicators of historic or active aquatic transport environments.
Field identification & locations
Commonly found in stream beds, riverbanks, and coastal beaches. Collectors can identify them by their smooth, rounded surfaces shaped by abrasion during transport.
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