sedimentary

Ferruginous Sandstone

Arenite with Iron Oxide cement (Fe2O3 / FeO(OH))

Hardness: 6-7 (Mohs scale), Color: Reddish-brown to dark chocolate, Luster: Dull/Earthy, Crystal Structure: Clastic granular texture, Cleavage: None (conchoidal to irregular fracture), Specific Gravity: 2.6-3.0

Identified June 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation and lithification of sand-sized silicate grains, specifically where iron-rich groundwater or fluids permeate the sediment, depositing hematite or limonite as a mineral cement. Often Paleozoic or Mesozoic in age.

Uses & applications

Used primarily as decorative building stone, road base material, and occasionally as a low-grade iron ore if the iron content is sufficiently high. Also valued by amateur geologists for teaching clastic textures.

Geological facts

The red colors of the Southwestern United States, such as those in the Grand Canyon or Sedona, are largely due to the same iron oxide minerals found in this specimen. It can sometimes contain fossil impressions due to its sedimentary nature.

Field identification & locations

Identified in the field by its gritty texture (feels like sandpaper), dark reddish stain that doesn't wash off, and its relatively high density compared to clean white sandstone. Commonly found in terrestrial or shallow marine sedimentary basins.

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