sedimentary
Ferruginous Sandstone
Clastic sedimentary rock (SiO2 with Fe2O3/FeO(OH) cement)
Hardness: 6-7 (Mohs scale), but can be crumbly; Color: Reddish-brown, tan, or ochre; Luster: Dull/Earthy; Structure: Clastic, granular; Specific Gravity: 2.0-2.6.
- Hardness
- 6-7 (Mohs scale), but can be crumbly
- Color
- Reddish-brown, tan, or ochre
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs scale), but can be crumbly; Color: Reddish-brown, tan, or ochre; Luster: Dull/Earthy; Structure: Clastic, granular; Specific Gravity: 2.0-2.6.
Formation & geological history
Formed by the accumulation of sand-sized minerals (quartz, feldspar) which are subsequently cemented together by iron oxides like hematite or goethite. These typically form in river beds, deserts, or marine environments over millions of years.
Uses & applications
Commonly used as building stone, pavers, or decorative landscaping rock. In some cases, high-iron varieties were historically used as a low-grade iron ore.
Geological facts
The distinct red and yellow coloring is essentially 'rusting' within the rock layers. Many of the famous arches and canyons in the American Southwest are composed of this type of sandstone.
Field identification & locations
Identify in the field by its gritty texture (feels like sandpaper) and its ability to leave a reddish streak if rubbed on a harder surface. Found globally in sedimentary basins.
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