igneous/sedimentary
River Stone (likely Basalt or Chert)
Silicon Dioxide (SiO2) for chert or Mafic Extrusive Rock for basalt
Hardness: 6-7 on Mohs scale; Color: Olive green to dark grey; Luster: Dull to waxy; Structure: Fine-grained (aphanitic) or cryptocrystalline; Specific Gravity: 2.6-3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- Olive green to dark grey
- Luster
- Dull to waxy
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Olive green to dark grey; Luster: Dull to waxy; Structure: Fine-grained (aphanitic) or cryptocrystalline; Specific Gravity: 2.6-3.0.
Formation & geological history
Formed from either volcanic activity (basalt) or chemical precipitation (chert). This specific specimen has been shaped and smoothed by fluvial (water) erosion in a river or stream over hundreds to thousands of years.
Uses & applications
Used in landscaping, construction aggregate (gravel), and as pocket stones for hobbyist collectors.
Geological facts
River stones represent the 'natural tumbling' process of geology. This shape, known as an ellipsoid, is the result of the stone hitting other rocks in moving water, wearing down sharp edges.
Field identification & locations
Identify in the field by its smooth, rounded edges and lack of visible large crystals. Commonly found in riverbeds, glacial deposits, and beaches. For collectors: look for unique colors or translucency when held to light.
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