sedimentary
Ferruginous Sandstone
Clastic sedimentary rock (primarily Quartz with Iron Oxide cement)
Hardness: 6-7 (Mohs scale); Color: Reddish-brown, tan, or ochre; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific gravity: 2.2–2.8
- Hardness
- 6-7 (Mohs scale)
- Color
- Reddish-brown, tan, or ochre
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Reddish-brown, tan, or ochre; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific gravity: 2.2–2.8
Formation & geological history
Formed by the accumulation of sand-sized grains (mostly quartz) cemented together by iron oxides (like hematite or goethite) deposited in terrestrial or shallow marine environments. Geological age varies widely from Paleozoic to Cenozoic eras.
Uses & applications
Used primarily in construction as a building stone or road aggregate. In some cases, it is used for decorative landscaping or as an iron ore source if the iron concentration is high enough.
Geological facts
The distinct red or brown color is due to the oxidation of iron minerals within the rock, a process often compared to 'rusting.' Many famous geological formations, such as those in the American Southwest, consist of types of ferruginous sandstone.
Field identification & locations
Identify by its gritty, sandpaper-like texture and its tendency to leave a reddish or yellowish streak if the iron oxide is soft. It is commonly found in desert environments, riverbeds, and ancient sea basins.
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