sedimentary
River Rocks and Pebbles
Mixed Silica-rich Sediments (SiO2 based)
Hardness: 6.5-7 (Mohs); Color: Tan, white, grey, brown, and pink; Luster: Dull to waxy; Crystal structure: Microcrystalline (Cryptocrystalline); Texture: Rounded to sub-rounded due to erosion.
- Hardness
- 6
- Color
- Tan, white, grey, brown, and pink
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Tan, white, grey, brown, and pink; Luster: Dull to waxy; Crystal structure: Microcrystalline (Cryptocrystalline); Texture: Rounded to sub-rounded due to erosion.
Formation & geological history
These specimens are primarily composed of quartz, chert, and quartzite. They were formed via the weathering of larger rock formations and subsequent transport by water (rivers or ancient glacial streams), which smoothed their edges over thousands of years.
Uses & applications
Commonly used for landscaping, decorative garden paths, concrete aggregate, and as 'pocket stones' for amateur collectors. Smoother pieces are sometimes used for rock painting or stone tumbling.
Geological facts
The smooth, rounded shape of these stones is a result of fluvial abrasion, where rocks bump into each other in moving water. Geologists use the roundness of such stones to estimate how far they have traveled from their original source.
Field identification & locations
Identify in the field by their water-worn, smooth surfaces and lack of sharp edges. They are found in riverbeds, beaches, and glacial till. For collectors, look for unique patterns or translucent 'agates' within the mix.
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