metamorphic or sedimentary
River Stone (Quartzite/Siltstone mixture)
Silicon Dioxide (SiO2) based metamorphosed sandstone
Hardness: 6-7 on Mohs scale; Color: Matte tan/grey; Luster: Dull to waxy; Texture: Smooth, water-worn/rounded; Cleavage: None (conchoidal fracture when broken)
- Hardness
- 6-7 on Mohs scale
- Color
- Matte tan/grey
- Luster
- Dull to waxy
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Matte tan/grey; Luster: Dull to waxy; Texture: Smooth, water-worn/rounded; Cleavage: None (conchoidal fracture when broken)
Formation & geological history
Formed through the cementation of fine mineral particles (sedimentary) or the metamorphosis of sandstone under heat and pressure. The rounded shape is a result of long-term fluvial erosion in a river or coastal environment.
Uses & applications
Used primarily in landscaping, decorative ground cover, aquarium substrates, and occasionally as a base material in construction of paths or mosaics.
Geological facts
River stones have been used since prehistoric times as tools, grinding stones, and weapons. Their smoothness is a chronological record of the distance they have traveled from their source rock.
Field identification & locations
Identified by its high sphericity and smoothness. Can be found in riverbeds, glacial outwashes, and beaches worldwide. Collectors often look for unique patterns or 'worry stone' textures.
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