sedimentary
Banded Iron Formation (BIF)
Banded Iron Formation
Hardness: 5-7 on Mohs scale; Color: alternating layers of silver-gray metallic (specularite), black (magnetite), and red, brown, or yellow (chert/jasper); Luster: metallic to earthy; Crystal structure: microcrystalline; Cleavage: none.
- Hardness
- 5-7 on Mohs scale
- Luster
- metallic to earthy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-7 on Mohs scale; Color: alternating layers of silver-gray metallic (specularite), black (magnetite), and red, brown, or yellow (chert/jasper); Luster: metallic to earthy; Crystal structure: microcrystalline; Cleavage: none.
Formation & geological history
Formed in ancient oceans during the Precambrian eons (mostly 3.8 to 1.8 billion years ago) through the precipitation of iron and silica as atmospheric oxygen levels rose (the Great Oxygenation Event).
Uses & applications
Primary source of iron ore globally for steel production; occasionally used as decorative stone or for cabochons in jewelry if highly jasplitic (rich in red jasper).
Geological facts
BIFs provide the main evidence for the timing of the Great Oxygenation Event; they are responsible for the vast majority of the world's iron ore reserves.
Field identification & locations
Can be identified in the field by its distinct alternating dark (iron-rich) and light (silica-rich) bands, high density/heaviness, and frequent magnetism if rich in magnetite. Found in ancient shield regions like the Pilbara (Australia) and Lake Superior (USA).
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 (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary