sedimentary
River Siltstone Pebble
Siltstone (composed mainly of silt-sized quartz and feldspar)
Hardness: 6-7 (Mohs scale), Color: Olive green to tan, Luster: Dull/Matte, Crystal structure: Microcrystalline, Cleavage: None, Specific gravity: 2.6-2.7
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Physical properties
Hardness: 6-7 (Mohs scale), Color: Olive green to tan, Luster: Dull/Matte, Crystal structure: Microcrystalline, Cleavage: None, Specific gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation and lithification of fine-grained silt particles in low-energy environments like river beds or lake bottoms. This specific specimen has been smoothed and rounded by water erosion.
Uses & applications
Used primarily as decorative landscaping gravel, in construction as fill material, or as a pocket stone for collectors of smooth river rocks.
Geological facts
Siltstone is intermediate between sandstone and shale. While it looks like clay, it feels gritty against the teeth, which is a classic field test for silt-sized particles.
Field identification & locations
Identify in the field by its very fine grain size (too small to see individual grains but larger than clay) and smooth, water-worn texture. Commonly found in riverbeds and on beaches.
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