sedimentary

Banded Iron Formation (BIF) / Jasper

Banded Iron Formation (primarily Quartz/SiO2 and Hematite/Fe2O3)

Hardness 6.5-7 on Mohs scale; color features alternating bands of red (jasper), silver-gray, or black; luster is waxy to vitreous; microcrystalline structure; conchoidal fracture; specific gravity 2.6-3.2 depending on iron content.

Identified June 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in ancient seawater billions of years ago (Precambrian) through the chemical precipitation of iron and silica. Triggered by early cyanobacteria releasing oxygen, reacting with dissolved iron in the oceans.

Uses & applications

Primary global source of iron ore; also used for decorative purposes, cabochons in jewelry, and as a popular lapidary material for collectors.

Geological facts

BIFs are time capsules of Earth's atmosphere; they provide the best evidence for the 'Great Oxidation Event' which occurred roughly 2.4 billion years ago. Famous deposits include the Hamersley Range in Australia and the Lake Superior region.

Field identification & locations

Identify by its heavy weight (due to iron), distinct parallel banding, and red/gray color palette. Found in ancient shield regions like the Iron Range in Minnesota, Michigan, Australia, and Brazil.

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