sedimentary

Siltstone with Sandstone Bands

Siltstone (composed of Quartz and Clay minerals)

AI-generated identification · may be incorrect

Hardness: 3-5 Mohs; Color: Gray, brownish-tan; Luster: Dull/Earthy; Texture: Fine-grained with visible layering; Cleavage: None (friable)

Hardness: 3-5 Mohs
Color: Gray, brownish-tan
Luster: Dull/Earthy

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 3-5 Mohs; Color: Gray, brownish-tan; Luster: Dull/Earthy; Texture: Fine-grained with visible layering; Cleavage: None (friable)

Formation & geological history

Formed from the deposition and lithification of silt and fine sand in low-energy aquatic environments such as river floodplains, deltas, or lakes over millions of years.

Uses & applications

Primarily used as fill material in construction or as low-quality building stone; occasionally used for garden landscaping.

Geological facts

Siltstone is intermediate between sandstone and shale. If individual grains are too small to be seen with the naked eye but feel gritty against the teeth, it is likely siltstone.

Field identification & locations

Look for distinct layering or 'bedding' and a gritty feel. Commonly found in sedimentary basins and along riverbanks where ancient sea levels have shifted.