sedimentary
River Stone (likely Siltstone or fine-grained Sandstone)
Clastic Sedimentary Rock (Lithic Wacke / Siltstone)
Hardness: 6-7 (Mohs); Color: Mottled gray, tan, and dark brown; Luster: Dull/Earthy; Structure: Fine-grained, clastic; Cleavage: None (conchoidal or irregular fracture); Specific Gravity: 2.6-2.7
- Hardness
- 6-7 (Mohs)
- Color
- Mottled gray, tan, and dark brown
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs); Color: Mottled gray, tan, and dark brown; Luster: Dull/Earthy; Structure: Fine-grained, clastic; Cleavage: None (conchoidal or irregular fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation and cementation of fine-grained mineral particles or rock fragments. The rounded shape indicates high-energy water transport (fluvial/river environment) and mechanical erosion over thousands of years.
Uses & applications
Common river stones are used for aquarium landscaping, garden decor, construction aggregate, and in 'worry stone' or decorative stone collecting.
Geological facts
River rocks are often much older than the landscape where they are found; the smooth surface is a result of millions of collisions with other rocks in moving water, acting like a natural rock tumbler.
Field identification & locations
Identify by its water-worn rounded edges and fine-grained texture. Found globally in riverbeds, glacial deposits, and beaches. Collectors look for unique banding or patterns caused by mineral impurities.
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