sedimentary
Banded Iron Formation (BIF)
Banded Iron Formation (SiO2 + Fe2O3)
Hardness: 5.5-7 (mohs); Color: alternating layers of silver-gray metallic hematite/magnetite and red jasper/chert; Luster: metallic to dull; Crystal Structure: microcrystalline; Specific Gravity: 3.0-5.0
- Hardness
- 5
- Luster
- metallic to dull
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 layers of silver-gray metallic hematite/magnetite and red jasper/chert; Luster: metallic to dull; Crystal Structure: microcrystalline; Specific Gravity: 3.0-5.0
Formation & geological history
Formed in ancient seawater billions of years ago (Archean to Proterozoic eons) when oxygen produced by cyanobacteria reacted with dissolved iron, causing it to precipitate as iron oxide layers on the ocean floor.
Uses & applications
Primary global source of iron ore for steel production; also used as a decorative stone in lapidary work and as a collectible geological specimen.
Geological facts
These rocks provide the most significant evidence for the 'Great Oxygenation Event' in Earth's history, showing when life first began drastically altering the atmosphere.
Field identification & locations
Identify by its distinct high-density (weight), magnetic properties if magnetite-rich, and characteristic red and black/gray stripes. Commonly found in ancient cratons like the Superior Upland (Lake Superior region) and Western Australia.
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