sedimentary
Ferruginous Sandstone (Ironstone)
Iron-rich Arenite
Hardness: 6-7 on Mohs scale; Color: Reddish-brown, rusty orange, dark grey to black; Luster: Dull, earthy, or metallic depending on iron content; Texture: Granular/Sandy.
- Hardness
- 6-7 on Mohs scale
- Color
- Reddish-brown, rusty orange, dark grey to black
- Luster
- Dull, earthy, or metallic depending on iron content
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Reddish-brown, rusty orange, dark grey to black; Luster: Dull, earthy, or metallic depending on iron content; Texture: Granular/Sandy.
Formation & geological history
Formed from the lithification of sand grains where iron oxides (hematite or goethite) act as the primary cementing agent. These often form in fluvial or shallow marine environments where iron-rich waters precipitate minerals between grains.
Uses & applications
Primary source of iron ore if concentration is high enough; used as building stone or decorative garden rock due to its distinctive color and resistance to weathering.
Geological facts
Ironstone was historically significant during the Industrial Revolution as a source of iron. Some specimens contain fossil impressions or 'liesegang rings' which are colorful, sub-parallel bands of iron precipitation.
Field identification & locations
Identify by its characteristic 'rusty' appearance and high density compared to normal sandstone. It is commonly found in sedimentary basins worldwide, particularly where ancient river systems existed.
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