sedimentary
Ferruginous Sandstone with Concretion
Sandstone (SiO2 dominated with Fe2O3 cement)
Hardness: 6-7 (quartz grains); Color: Reddish-brown, tan, or grey; Luster: Dull/Earthy; Structure: Clastic with nodular/concretionary forms; Cleavage: None; Specific Gravity: 2.2-2.8.
- Hardness
- 6-7 (quartz grains)
- Color
- Reddish-brown, tan, or grey
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (quartz grains); Color: Reddish-brown, tan, or grey; Luster: Dull/Earthy; Structure: Clastic with nodular/concretionary forms; Cleavage: None; Specific Gravity: 2.2-2.8.
Formation & geological history
Formed through the accumulation and compaction of sand grains (usually quartz) cemented by iron oxides. These iron minerals often precipitate in groundwater, sometimes forming odd shapes or concretions around a core nucleus.
Uses & applications
Primarily used in construction (decorative stone, aggregate) or as an ornamental specimen for collectors interested in pseudofossils or concretions.
Geological facts
These specimens are often mistaken for fossils, bones, or even footprints because of their strange weather-rounded shapes and iron-rich 'cast-like' appearance, leading to the nickname 'pseudofossils'.
Field identification & locations
Commonly found in sedimentary basins and riverbeds where iron-rich groundwater is present. Identify by its grainy texture, reddish 'rust' staining, and lack of internal organic bone structure.
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