sedimentary

Banded Iron Formation (Chert)

Banded Iron Formation (BIF) with Jasper/Chert layers

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Red (Jasper), Black (Magnetite/Hematite), or Gray; Luster: Dull to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9

Hardness: 6
Color: Red (Jasper), Black (Magnetite/Hematite), or Gray
Luster: Dull to vitreous

Identified June 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in ancient oceans between 3.8 and 1.8 billion years ago (Precambrian) through the precipitation of iron and silica due to oxygen produced by early cyanobacteria.

Uses & applications

Major source of iron ore globally; used in jewelry as Jasper; or as lapidary material for decorative carvings and cabochons.

Geological facts

Banded iron formations provide critical evidence for the 'Great Oxidation Event,' showing when oxygen first began to accumulate in Earth's atmosphere.

Field identification & locations

Identify by distinct banding of red and dark gray/black layers; often heavy for its size if iron content is high. Found in ancient cratonic areas like the Lake Superior region, Australia, and South Africa.