sedimentary

Banded Siltstone or Mudstone

Clastic Sedimentary Rock (Siltstone/Argillite)

Hardness: 3-5 on Mohs scale. Color: Greenish-grey and reddish-brown bands. Luster: Dull/Earthy. Texture: Fine-grained, smooth to the touch, clastic. Structure: Distinct parallel bedding or laminations.

Hardness: 3-5 on Mohs scale
Color: Greenish-grey and reddish-brown bands
Luster: Dull/Earthy

Identified July 18, 2026More sedimentary →

Explore Banded Siltstone or Mudstone in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed through the deposition and lithification of fine-grained clay and silt particles in low-energy environments like lake beds or deep ocean basins. The colors result from oxidation states of iron (red for ferric, green for ferrous).

Uses & applications

Primarily used as decorative stones, in lapidary work for cabochons or tumbled stones, and sometimes in landscaping. Historically used for making simple tools or ornaments.

Geological facts

The distinct banding is known as rhythmite, which can represent seasonal changes in sediment deposition. This specific color contrast is often seen in Precambrian or Paleozoic formations.

Field identification & locations

Can be identified by the fine-grained texture that lacks the visible grains of sandstone and the rhythmic color banding. Commonly found in riverbeds and glacial deposits where they have been water-worn into smooth pebbles.

Other sedimentary specimens

See all

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Sedimentary Sandstone

Arenite (Sedimentary Rock)

sedimentary

Fossiliferous Concretion

Septarian Concretion containing Brachiopods/Crinoids

fossil

Shale

Shale (clastic sedimentary rock)

sedimentary

Brown Sandstone (River Rock)

Arenite

sedimentary

Shale

Argillaceous sedimentary rock

sedimentary