sedimentary
Banded Iron Formation
Banded Iron Formation (BIF)
Hardness: 5.5 to 6.5 on the Mohs scale; Color: Distinct alternating bands of black (magnetite or hematite), red/brown (hematite or jasper), and grey/white (quartz or chert); Luster: Vitreous to metallic on polished surfaces; Crystal structure: Microcrystalline quartz with iron oxides; Cleavage: None;…
- Hardness
- 5
- Luster
- Vitreous to metallic on polished surfaces
Identified More sedimentary →
Explore Banded Iron Formation in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5.5 to 6.5 on the Mohs scale; Color: Distinct alternating bands of black (magnetite or hematite), red/brown (hematite or jasper), and grey/white (quartz or chert); Luster: Vitreous to metallic on polished surfaces; Crystal structure: Microcrystalline quartz with iron oxides; Cleavage: None; Specific Gravity: 3.2 to 5.0 depending on iron content.
Formation & geological history
Formed in marine environments primarily during the Precambrian era (mostly between 2.4 and 1.8 billion years ago) when dissolved iron in Earth's oceans oxidized and precipitated out as oxygen was progressively released by photosynthetic cyanobacteria.
Uses & applications
Primary global ore for the extraction of iron and steel production; also used as a decorative stone, lapidary material, and in polished specimens for mineral collectors.
Geological facts
Banded Iron Formations represent one of the most significant geological milestones in Earth's history, directly recording the Great Oxidation Event when atmospheric and oceanic oxygen levels spiked.
Field identification & locations
Easily identified by its striking multi-colored red, black, and grey stripes. Commonly found in ancient cratons and shields such as the Lake Superior region in North America, Western Australia, South Africa, and Brazil.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Banded Siltstone / Mudstone Pebble
Siltstone / Argillite
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary