sedimentary
River Stone / Siltstone
Siltstone (composed of lithified silt)
Hardness: 3-5 on Mohs scale; Color: Grayish-green or tan; Luster: Dull/Earthy; Crystal Structure: Clastic (microscopic grains); Cleavage: None; Specific Gravity: ~2.6.
- Hardness
- 3-5 on Mohs scale
- Color
- Grayish-green or tan
- Luster
- Dull/Earthy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3-5 on Mohs scale; Color: Grayish-green or tan; Luster: Dull/Earthy; Crystal Structure: Clastic (microscopic grains); Cleavage: None; Specific Gravity: ~2.6.
Formation & geological history
Formed from the accumulation and lithification of silt-sized particles (larger than clay but smaller than sand) in calm water environments like floodplains or lake beds. This specimen has been rounded by fluvial (river) erosion.
Uses & applications
Used in landscaping, decorative aquariums, and occasionally as a base material in construction. Polished versions are used for 'worry stones' or decorative crafts.
Geological facts
Siltstones are distinct from sandstones by their finer grain size and from shales by their lack of fissility (the ability to split into thin layers). Many river stones can be millions of years old, traveling miles from their original source.
Field identification & locations
Identify in the field by its smooth, river-worn texture and fine-grained matte surface. It should feel slightly gritty to the tongue or teeth unlike clay-based rocks. Commonly found in riverbeds, glacial deposits, and coastal areas.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary