sedimentary
Banded Iron Formation (BIF) / Tiger Iron
Banded Iron Formation containing Hematite (Fe2O3) and Magnetite (Fe3O4)
Hardness: 5.5-7 (Mohs), Color: Alternating bands of silver-grey (hematite), black (magnetite), and often red (jasper), Luster: Metallic to sub-metallic, Structure: Banded/laminated
- Hardness
- 5
- Luster
- Metallic to sub-metallic, Structure: Banded/laminated
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5.5-7 (Mohs), Color: Alternating bands of silver-grey (hematite), black (magnetite), and often red (jasper), Luster: Metallic to sub-metallic, Structure: Banded/laminated
Formation & geological history
Formed in marine environments during the Precambrian era (approx. 2.4 to 1.8 billion years ago) through the precipitation of iron oxides and silica as oxygen levels rose in Earth's atmosphere
Uses & applications
Primary global source of iron ore for steel production; decorative use in lapidary, jewelry, and as ornamental stone
Geological facts
These formations reflect the 'Great Oxygenation Event' when early life began producing oxygen through photosynthesis, causing dissolved iron in the oceans to rust and settle on the seafloor
Field identification & locations
Identify by distinct rhythmic layering of heavy metallic bands and silica; highly magnetic if magnetite-rich; found in ancient cratons like the Pilbara (Australia) or Lake Superior (USA)
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary