sedimentary

Shale with Limonite/Hematite Staining

Argillaceous sedimentary rock with Iron Oxides (FeO(OH)·nH2O / Fe2O3)

AI-generated identification · may be incorrect

Hardness: 3-4 (excluding coatings); Color: Reddish-brown, yellowish-orange, and dark brown; Luster: Dull to sub-metallic when wet; Crystal structure: Amorphous or microcrystalline coatings; Cleavage: Fissile (splits into thin layers).

Hardness: 3-4 (excluding coatings)
Color: Reddish-brown, yellowish-orange, and dark brown
Luster: Dull to sub-metallic when wet

Identified June 24, 2026More sedimentary →

Explore Shale with Limonite/Hematite Staining 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 lithification of mud and clay particles in low-energy environments like river deltas or lake beds. The vibrant colors are caused by the oxidation (rusting) of iron-rich minerals within the rock, often occurring in various geological eras from Paleozoic to Cenozoic.

Uses & applications

Common shale is used as a source for natural gas (fracking), in the production of bricks, cement, and pottery. Iron-stained specimens are primarily of interest to amateur collectors or used as decorative garden stones.

Geological facts

The reddish-brown 'stains' are essentially geological rust. When iron-bearing minerals are exposed to water and oxygen, they transform into limonite or hematite, often preserving the layered structure of the host rock.

Field identification & locations

Identify in the field by its thin, plate-like bedding and the way it easily crumbles or flakes. It is commonly found in riverbeds, canyons, and road cuts through sedimentary basins. Collectors look for unique banding patterns caused by the iron oxidation.