sedimentary

Siltstone Pebble

Siltstone (composed of microscopic quartz and clay minerals)

AI-generated identification · may be incorrect

Hardness: 3-5 (Mohs scale); Color: Brownish-grey to olive-green; Luster: Dull/Earthy; Texture: Fine-grained, gritty feeling on teeth; Structure: Clastic

Hardness: 3-5 (Mohs scale)
Color: Brownish-grey to olive-green
Luster: Dull/Earthy

Identified July 2, 2026More sedimentary →

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Physical properties

Hardness: 3-5 (Mohs scale); Color: Brownish-grey to olive-green; Luster: Dull/Earthy; Texture: Fine-grained, gritty feeling on teeth; Structure: Clastic

Formation & geological history

Formed from the compaction and cementation of silt-sized particles in low-energy environments like river floodplains or lake beds. This specimen has been rounded and smoothed by water erosion.

Uses & applications

Used primarily as road base, construction fill, or decorative river rock in landscaping.

Geological facts

Siltstone is intermediate between sandstone and shale; it has smaller grains than sandstone but lacks the fissility (layer-splitting property) of shale.

Field identification & locations

Commonly found in riverbeds and glacial deposits. Identification is made by its smooth water-worn surface and a grain size that is too fine to see with the naked eye but feels abrasive.