sedimentary
Sandstone River Cobble
Arenite (predominantly SiO2)
Hardness: 6-7 (Mohs scale); Color: Tan, beige, or light brown with distinct dark horizontal banding; Luster: Dull/Earthy; Texture: Granular and clastic; Structure: Rounded by water erosion (cobble).
- Hardness
- 6-7 (Mohs scale)
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Tan, beige, or light brown with distinct dark horizontal banding; Luster: Dull/Earthy; Texture: Granular and clastic; Structure: Rounded by water erosion (cobble).
Formation & geological history
Formed through the accumulation and cementation of mineral grains or rock fragments (0.0625 to 2 mm in size) over millions of years. This specific specimen has been rounded and smoothed by the abrasive action of water in a river or coastal environment.
Uses & applications
Used primarily in landscaping, decorative stone for gardens, and construction fill. In high-quality forms, sandstone is a popular dimension stone for buildings.
Geological facts
The dark bands visible are likely heavy mineral layers or iron oxides that settled during the deposition process, providing a 'snapshot' of the ancient environment's energy levels.
Field identification & locations
Identified by its gritty feel (like sandpaper) and visible sand-sized grains. Found globally in riverbeds, glacial deposits, and beaches. Collectors should look for unique banding or internal structures like cross-bedding.
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