sedimentary
Ferruginous Sandstone
Arenite with Iron-oxide cement (composed of Quartz and Limonite/Hematite)
Hardness: 6-7 (sand grains) but matrix can crumble; Color: Reddish-brown, earthy tan, rust; Luster: Dull, earthy; Crystal structure: Granular clastic; Cleavage: None; Specific gravity: 2.2–2.8
- Hardness
- 6-7 (sand grains) but matrix can crumble
- Color
- Reddish-brown, earthy tan, rust
- Luster
- Dull, earthy
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Physical properties
Hardness: 6-7 (sand grains) but matrix can crumble; Color: Reddish-brown, earthy tan, rust; Luster: Dull, earthy; Crystal structure: Granular clastic; Cleavage: None; Specific gravity: 2.2–2.8
Formation & geological history
Formed through the accumulation of sand-sized mineral particles or rock fragments, subsequently cemented together by iron oxides (like limonite or hematite) precipitated from groundwater. Commonly found in terrestrial or shallow marine environments.
Uses & applications
Used primarily in construction for building stone and road base. Occasionally used as a low-grade iron ore if iron content is high enough. Popular among hobbyists for its rustic aesthetic.
Geological facts
The red and brown colors are effectively 'rusting' minerals within the stone. These rocks are responsible for many of the world's famous red rock landscapes, such as those in Sedona, Arizona and the Australian Outback.
Field identification & locations
Identify by its gritty, sandpaper-like texture and its tendency to leave a reddish or yellowish streak if scratched. Very common in sedimentary basins worldwide. When wet, the reddish hues often become much more vibrant.
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