sedimentary

Banded Iron Formation (BIF)

Banded Iron Formation (predominantly Hematite and Chert)

Hardness: 5-7 Mohs; Color: Alternating red, brown, and steel-grey layers; Luster: Dull to metallic (hematite layers) and vitreous (chert layers); Structure: Distinctly layered or laminated; Specific Gravity: 3.0-5.0.

Hardness: 5-7 Mohs
Color: Alternating red, brown, and steel-grey layers

Identified July 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in ancient seawater during the Archean and Proterozoic eons (2.4 to 1.8 billion years ago) through the precipitation of iron oxides and silica as oxygen levels in the atmosphere began to rise due to cyanobacteria.

Uses & applications

The primary source of iron ore for the global steel industry. Also used for ornamental carvings, landscaping, and as a collectible geological specimen.

Geological facts

BIFs represent a significant snapshot of the 'Great Oxidation Event' in Earth's history. They provided the iron that fueled the Industrial Revolution.

Field identification & locations

Identify by looking for rhythmic layering of dark, heavy metallic minerals and lighter, silica-rich bands. Often found in ancient cratons like the Superior Upland (USA/Canada), Western Australia, and South Africa.

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