sedimentary
Ironstone (possibly Bog Iron or Limonite)
Goethite-rich Ironstone (FeO(OH))
Hardness: 4.0 - 5.5; Color: Dark brown to reddish-brown; Luster: Dull to sub-metallic; Crystal Structure: Usually massive or earthy; Cleavage: None; Specific Gravity: 3.3 - 4.3
- Hardness
- 4
- Color
- Dark brown to reddish-brown
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 4.0 - 5.5; Color: Dark brown to reddish-brown; Luster: Dull to sub-metallic; Crystal Structure: Usually massive or earthy; Cleavage: None; Specific Gravity: 3.3 - 4.3
Formation & geological history
Formed by the precipitation of iron oxides from groundwater or surface water, often in boggy, swampy, or shallow marine environments. These specimens can range from recent Holocene deposits to millions of years old.
Uses & applications
Historically used as a low-grade iron ore; currently used in construction as road metal or as architectural stone; sometimes used as a pigment (ochre).
Geological facts
Ironstone nodules like this were a primary source of iron for the early industrial revolution. The dark, porous texture is characteristic of many bog iron deposits found in North America and Europe.
Field identification & locations
Identify by its high density (feels heavy for its size), dark brown streak, and lack of magnetism (unless containing magnetite). Commonly found in areas with iron-rich soils or wetlands.
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