sedimentary
Brown Pebble (River Rock)
Indeterminate (Likely Silicon Dioxide / Quartz-rich)
Hardness: ~7 (Mohs), Color: Earthy brown to reddish-brown, Luster: Dull to matte (sub-vitreous if wet), Crystal Structure: Microcrystalline (Cryptocrystalline), Cleavage: None/Conchoidal fracture
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Physical properties
Hardness: ~7 (Mohs), Color: Earthy brown to reddish-brown, Luster: Dull to matte (sub-vitreous if wet), Crystal Structure: Microcrystalline (Cryptocrystalline), Cleavage: None/Conchoidal fracture
Formation & geological history
Formed through the erosion and weathering of larger rock formations, transported by water (rivers, streams, or glacial melt) which rounds the edges over centuries. Likely composed of chert, jasper, or weathered quartz.
Uses & applications
Landscaping, decorative garden mulch, industrial abrasives when crushed, or historical use as primitive tools (celt/scrapers).
Geological facts
The smooth, rounded shape is a result of fluvial abrasion, where rocks tumble together in running water. They are some of the most common geological finds worldwide.
Field identification & locations
Identify by its smooth, water-worn texture and lack of sharp edges. Commonly found in riverbeds, floodplains, and gravel pits. Collectors often look for unique colors or banding within these common shapes.
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