sedimentary

Banded Iron Formation (BIF) / Jasper

Banded Iron Formation (SiO2 with Fe2O3 / Fe3O4)

Hardness: 6.5-7 on Mohs scale; Color: Alternating red, brown, pink, and grey-black layers; Luster: Dull to earthy or sub-metallic; Structure: Fine-grained microcrystalline quartz (jasper) and iron oxides (hematite/magnetite)

Hardness: 6
Color: Alternating red, brown, pink, and grey-black layers
Luster: Dull to earthy or sub-metallic

Identified July 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in ancient ocean basins during the Precambrian era (2.4 to 1.8 billion years ago) when photosynthesizing cyanobacteria released oxygen into iron-rich waters, causing iron minerals to precipitate in distinct alternating layers with silica.

Uses & applications

Major global source of iron ore (steel production); lapidary work, cabochons, decorative carvings, and geological educational collections.

Geological facts

Banded Iron Formations mark the 'Great Oxidation Event' in Earth's early history, recording the point when free oxygen first accumulated in the oceans and atmosphere.

Field identification & locations

Identified by distinct alternating layers of red jasper/chert and dark iron oxides; noticeably heavy due to iron content; commonly found in Precambrian shield regions like Lake Superior, Western Australia, South Africa, and Canada.

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