sedimentary
River Siltstone Pebble
Siltstone (SiO2, Al2Si2O5(OH)4 mix)
Hardness: 3-5 Mohs; Color: Tan, brown, or buff; Luster: Dull/Earthy; Crystal structure: Clastic (microscopic); Cleavage: None/Irregular; Specific Gravity: 2.3-2.6
- Hardness
- 3-5 Mohs
- Color
- Tan, brown, or buff
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3-5 Mohs; Color: Tan, brown, or buff; Luster: Dull/Earthy; Crystal structure: Clastic (microscopic); Cleavage: None/Irregular; Specific Gravity: 2.3-2.6
Formation & geological history
Formed from the lithification of silt-sized particles deposited in low-energy environments like river beds or lake bottoms, then smoothed by water erosion.
Uses & applications
Primarily used as aggregate in construction, landscaping, or as a decorative garden stone.
Geological facts
Siltstone is intermediate between sandstone and shale; it has smaller grains than sandstone but lacks the fissility (layering) of shale.
Field identification & locations
Identify by its fine-grained, gritty feel (like fine sandpaper) and lack of visible crystals. Commonly found in riverbeds and glacial till.
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