sedimentary
Ferruginous Sandstone
Arenite with Iron Oxide matrix (Fe2O3)
Hardness: 6-7 (Mohs scale), Color: Reddish-brown, tan, and dark streaks, Luster: Dull to earthy, Structure: Granular/clastic, Cleavage: None, Specific Gravity: 2.3–2.8
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Physical properties
Hardness: 6-7 (Mohs scale), Color: Reddish-brown, tan, and dark streaks, Luster: Dull to earthy, Structure: Granular/clastic, Cleavage: None, Specific Gravity: 2.3–2.8
Formation & geological history
Formed in high-energy sedimentary environments like beaches or river beds where sand grains are cemented together by iron-rich minerals. Often found in strata dating back to the Paleozoic or Mesozoic eras.
Uses & applications
Commonly used as a building stone or decorative aggregate. Historically used by various cultures to extract iron ore or as a carving material.
Geological facts
The reddish color is due to the presence of hematite or limonite, which acts as the 'glue' holding the sand grains together. It is often a key indicator of ancient oxygenated environments.
Field identification & locations
Identify in the field by its sandy texture and the way it stains hands slightly orange-red when rubbed. Found in areas with exposed sedimentary outcrop such as the Appalachian or Rocky Mountains.
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