sedimentary
Ferruginous Sandstone
Sandstone with iron oxide (Hematite/Limonite) cement
Hardness: 6-7 (Mohs); Color: Reddish-brown, earthy tan, and orange; Luster: Dull/Earthy; Crystal Structure: Clastic (grainy); Specific Gravity: 2.3-2.6
- Hardness
- 6-7 (Mohs)
- Color
- Reddish-brown, earthy tan, and orange
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs); Color: Reddish-brown, earthy tan, and orange; Luster: Dull/Earthy; Crystal Structure: Clastic (grainy); Specific Gravity: 2.3-2.6
Formation & geological history
Formed through the accumulation and cementation of sand-sized grains, specifically silica-rich grains bound by iron oxide minerals. Usually found in ancient riverbeds or marine environments where oxygen-rich water interacts with iron.
Uses & applications
Used primarily in building construction as cladding or pavers, and occasionally as a source of iron ore in low-grade deposits. Valued by collectors for its color variations.
Geological facts
The reddish color is primarily due to the presence of Hematite. It is often a key component of 'Red Bed' geological formations which signify oxidizing atmospheric conditions during formation.
Field identification & locations
Identify by its gritty, sandpaper-like texture and its tendency to leave a reddish streak if rubbed on a harder surface. Common in Southwest USA, Australia, and various basin regions.
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