metamorphic
Riverstone (likely Gray Slate or Siltstone)
Metamorphosed fine-grained sedimentary rock (Argillite/Slate)
Hardness: 2.5-4 Mohs; Color: Dull gray to grayish-green; Luster: Matte to slightly waxy; Structure: Fine-grained, microcrystalline; Cleavage: Slaty cleavage often present.
- Hardness
- 2
- Color
- Dull gray to grayish-green
- Luster
- Matte to slightly waxy
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Physical properties
Hardness: 2.5-4 Mohs; Color: Dull gray to grayish-green; Luster: Matte to slightly waxy; Structure: Fine-grained, microcrystalline; Cleavage: Slaty cleavage often present.
Formation & geological history
Formed through the low-grade metamorphism of clay-rich sedimentary rocks (shale). The smooth, rounded shape is the result of water erosion in a river or coastal environment.
Uses & applications
Used primarily for decorative landscaping, aquarium stones, or as worry stones. Higher-grade slate is used for roofing and flooring.
Geological facts
The smooth texture of these stones makes them popular for rock painting and home decor. They are essentially 'weathered fragments' of larger geological formations transported by water.
Field identification & locations
Identify by its smooth, water-worn surface and fine-grained texture. It lacks visible crystals. Commonly found in riverbeds and along beaches throughout North America and Europe.
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