sedimentary

Red Siltstone

Siltstone

Hardness: 3 to 4 on the Mohs scale. Color: Reddish brown due to iron oxide (hematite) staining. Luster: Dull or earthy. Crystal structure: Clastic/microcrystalline, composed mainly of quartz and clay minerals with grain sizes between 0.002 and 0.063 mm.…

Hardness: 3 to 4 on the Mohs scale
Color: Reddish brown due to iron oxide (hematite) staining
Luster: Dull or earthy

Identified July 30, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the accumulation, compaction, and lithification of silt-sized mineral particles, typically in low-energy environments such as river floodplains, deltas, lakes, or deep-marine settings. Geological age ranges widely from Precambrian to recent.

Uses & applications

Used primarily in landscaping, crushed stone for construction, and occasionally as decorative building stone.

Geological facts

Red siltstone often preserves fine sedimentary structures like ripple marks and mud cracks, providing geologists with detailed clues about ancient environments.

Field identification & locations

Identified in the field by its fine-grained texture that feels slightly gritty between the teeth (distinguishing it from smoother shale), its distinct reddish-brown color, and lack of visible individual crystals without a microscope.