sedimentary

Red Siltstone

Siltstone (primarily quartz and feldspar sized 0.0039 to 0.0625 mm)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs); Color: Reddish-brown due to iron oxide (hematite); Luster: Dull/Earthy; Crystal structure: Clastic (microcrystalline quartz); Cleavage: None/Planar bedding; Specific gravity: 2.6

Hardness: 3-4 (Mohs)
Color: Reddish-brown due to iron oxide (hematite)
Luster: Dull/Earthy

Identified May 7, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the deposition and lithification of silt-sized particles in low-energy aquatic environments like floodplains, lake beds, or marine shelves. Often represents geological periods like the Devonian or Triassic.

Uses & applications

Used primarily as low-grade fill in construction, aggregate for road bases, and occasionally as decorative garden stones or rustic interior flagstones.

Geological facts

Siltstones are midway between sandstones and shales; they are distinguished from shales by their lack of fissility (the ability to split into thin layers). The red color indicates oxygen was present during formation.

Field identification & locations

Identify in the field by its fine-grained texture (gritty to the teeth but smooth to the touch) and lack of visible grains. It is commonly found in sedimentary basins worldwide.