sedimentary
Sandstone Pebble (River Rock)
Sandstone (Quartz-rich sedimentary rock with iron oxide staining)
Hardness: 6-7 on the Mohs scale (due to quartz grains). Color: Light tan, greyish-beige with brownish-red iron oxide mineral staining on the surface. Luster: Dull, earthy. Texture: Medium-grained, gritty to the touch like sandpaper. Structure: Rounded cobblestone/pebble shape formed by water erosion.
- Hardness
- 6-7 on the Mohs scale (due to quartz grains)
- Luster
- Dull, earthy
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Physical properties
Hardness: 6-7 on the Mohs scale (due to quartz grains). Color: Light tan, greyish-beige with brownish-red iron oxide mineral staining on the surface. Luster: Dull, earthy. Texture: Medium-grained, gritty to the touch like sandpaper. Structure: Rounded cobblestone/pebble shape formed by water erosion.
Formation & geological history
Formed from the compaction and cementation of sand-sized grains of mineral, rock, or organic material over millions of years, typically in river, lake, or ocean environments. The smooth, rounded shape indicates transport and weathering by river or stream action.
Uses & applications
Commonly used in landscaping, river rock garden decoration, construction aggregate, and acquarium decoration. Plain beach/river pebbles hold little commercial value as individual geological specimens.
Geological facts
The distinct reddish-brown pattern on the surface is a manganese or iron oxide stain, often formed when mineral-rich water seeps into tiny pores or fractures in the rock. Iron oxide stains are the same natural rust compounds that give many rocks their reddish hue.
Field identification & locations
Identified by its gritty sandpaper texture, light tan color, and water-worn smooth contour. Found in riverbeds, lake shores, glacial deposits, and gravel pits worldwide. Easy to collect for crafts, rock painting, or landscaping.
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