sedimentary
Red Sandstone (Iron-rich)
Ferruginous Sandstone (SiO2 with Iron Oxides)
Hardness: 6-7 (Mohs scale), Color: Rusty red to orange due to hematite/limonite staining, Luster: Dull or earthy, Crystal structure: Clastic (grainy), Cleavage: None
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Physical properties
Hardness: 6-7 (Mohs scale), Color: Rusty red to orange due to hematite/limonite staining, Luster: Dull or earthy, Crystal structure: Clastic (grainy), Cleavage: None
Formation & geological history
Formed by the accumulation of sand-sized mineral particles (quartz) cemented together by mineral matter. The red color suggests deposition in an oxygenated terrestrial environment (oxidizing conditions), often during the Triassic or Permian periods.
Uses & applications
Historically used in construction and architecture (famous brownstones), landscaping, and as an abrasive material. Finely ground iron-rich varieties were also used as early pigments.
Geological facts
The red color is caused by the presence of iron oxide (rust) which coats the individual grains of sand. This process is common in desert and river basin deposits.
Field identification & locations
Identify in the field by its distinct grainy texture (resembles sandpaper) and its ability to leave a reddish streak if rubbed. Found globally in large basins like the American Southwest or Northern England.
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