sedimentary
Ferruginous Sandstone (Ironstone)
Ferruginous arenite
Hardness: 6-7 (Mohs); Color: Dark brown, reddish-brown, or rusty; Luster: Dull/Earthy; Structure: Clastic, fine to medium-grained; Cleavage: None; Specific Gravity: 2.5-3.0
- Hardness
- 6-7 (Mohs)
- Color
- Dark brown, reddish-brown, or rusty
- Luster
- Dull/Earthy
Identified More sedimentary →
Explore Ferruginous Sandstone (Ironstone) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 (Mohs); Color: Dark brown, reddish-brown, or rusty; Luster: Dull/Earthy; Structure: Clastic, fine to medium-grained; Cleavage: None; Specific Gravity: 2.5-3.0
Formation & geological history
Formed through the lithification of sand grains where iron oxides (like hematite or goethite) act as the primary cementing agent. Often found in ancient riverbeds or marine environments.
Uses & applications
Used as a construction material, an iron ore source in historical times, and for architectural stone. Collectors value unusual weathering patterns.
Geological facts
This rock gets its dark color from the oxidation of iron. In desert environments, these rocks often develop a 'desert varnish' which makes them appear almost black or metallic.
Field identification & locations
Identify by its heavy weight (due to iron content), grainy texture, and distinctive reddish-brown streak. Common in arid regions or areas with high iron-rich groundwater.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
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
Mudstone
Argillite / Siliciclastic sedimentary rock
sedimentary