igneous
River Stone (likely Andesite or Siltstone)
Intermediate Volcanic Rock / Fine-grained Sedimentary Rock
Hardness: 5.5-7 (Mohs); Color: Dark grey to brownish-grey; Luster: Dull/Earthy; Crystal structure: Fine-grained/Aphanitic; Shape: Sub-rounded due to water erosion.
- Hardness
- 5
- Color
- Dark grey to brownish-grey
- Luster
- Dull/Earthy
Identified More igneous →
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Physical properties
Hardness: 5.5-7 (Mohs); Color: Dark grey to brownish-grey; Luster: Dull/Earthy; Crystal structure: Fine-grained/Aphanitic; Shape: Sub-rounded due to water erosion.
Formation & geological history
Formed either through volcanic cooling or sediment lithification, then shaped over centuries by the hydraulic action of river or stream currents.
Uses & applications
Used primarily in landscaping, decorative ground cover, construction aggregate, and as 'worry stones' for stress relief.
Geological facts
River stones have been used since prehistoric times as basic tools, grinding stones, and weapons. Their smooth shape is a direct result of 'abrasion,' where rocks collide and wear each other down in moving water.
Field identification & locations
Identify by its smooth, water-worn texture and rounded edges. Commonly found in riverbeds, glacial till, and coastal areas.
