sedimentary
Banded Iron Formation (BIF)
Magnetite-Hematite Chert (Banded Iron Formation)
Hardness: 5-7 (Mohs scale), Color: alternating bands of silver-grey to black (iron oxides) and red, yellow, or brown (chert/jasper), Luster: Metallic to earthy, Crystal Structure: Trigonal/Hexagonal systems in microcrystalline form, Cleavage: None.
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-7 (Mohs scale), Color: alternating bands of silver-grey to black (iron oxides) and red, yellow, or brown (chert/jasper), Luster: Metallic to earthy, Crystal Structure: Trigonal/Hexagonal systems in microcrystalline form, Cleavage: None.
Formation & geological history
Formed in ancient marine environments between 2.4 and 1.8 billion years ago (Proterozoic Eon) through the precipitation of iron from seawater triggered by oxygen released by early photosynthetic bacteria (cyanobacteria).
Uses & applications
Primary global source of iron ore for steel production; occasionally used as decorative stone or lapidary material when aesthetically colorful.
Geological facts
These rocks represent the 'Great Oxygenation Event' in Earth's history, documenting the transition of our atmosphere from anaerobic to aerobic.
Field identification & locations
Identify by its high density (heavy for its size), distinct color layering, and magnetism (if magnetite is present). Commonly found in the Lake Superior region (USA/Canada), Western Australia (Pilbara), and South Africa.
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