sedimentary
Banded Iron Formation (BIF)
Magnetite-hematite-chert formation
Hardness: 5-7 (Mohs), Color: Alternating bands of silver-black (iron) and reddish-yellow/brown (chert/jasper), Luster: Metallic to dull, Crystal Structure: Trigonal/Hexagonal, Cleavage: None/Conchoidal.
Identified More sedimentary →
Explore Banded Iron Formation (BIF) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-7 (Mohs), Color: Alternating bands of silver-black (iron) and reddish-yellow/brown (chert/jasper), Luster: Metallic to dull, Crystal Structure: Trigonal/Hexagonal, Cleavage: None/Conchoidal.
Formation & geological history
Formed in marine environments as chemical precipitates when photosynthetic oxygen reacted with dissolved iron in Earth's early oceans. Most date to the Archean or Proterozoic Eons (3.8 to 1.8 billion years ago).
Uses & applications
Predominant global source of iron ore for steel production; lapidary use for decorative carvings and jewelry stones like Tiger Iron.
Geological facts
They represent the transition of Earth's atmosphere from oxygen-poor to oxygen-rich, known as the Great Oxidation Event.
Field identification & locations
Identify by heavy weight (high specific gravity), magnetism (if magnetite is present), and visible alternating layers of metallic iron oxides and silica. Common in Western Australia, Brazil, and the Lake Superior region.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary