sedimentary
Ironstone Concretion
Siderite or Hematite Concretion (FeCO3 or Fe2O3)
Hardness: 4-6 on Mohs scale; Color: Rusty brown, tan, or dark red; Luster: Dull to earthy; Structure: Concentric layering (liesegang rings); Cleavage: None; Specific Gravity: 3.0-4.0
- Hardness
- 4-6 on Mohs scale
- Color
- Rusty brown, tan, or dark red
- Luster
- Dull to earthy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 4-6 on Mohs scale; Color: Rusty brown, tan, or dark red; Luster: Dull to earthy; Structure: Concentric layering (liesegang rings); Cleavage: None; Specific Gravity: 3.0-4.0
Formation & geological history
Formed by the precipitation of mineral cement within the spaces between sediment grains, often around a nucleus like a leaf or shell. These typically form in sedimentary basins over millions of years.
Uses & applications
Historically used as a low-grade iron ore; commonly collected as geological curiosities or used in landscaping and garden decoration.
Geological facts
Small, round ironstone concretions found on Mars are nicknamed 'blueberries,' providing evidence of past water on the planet. On Earth, they are often mistaken for fossils or meteorites due to their unusual shapes.
Field identification & locations
Identify in the field by looking for rounded or 'pill-shaped' nodules that are significantly heavier and harder than the surrounding sandstone or shale. They often exhibit 'onion-skin' weathering layers.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary