sedimentary

Banded Iron Formation (BIF) / Iron Ore

Hematite-Magnetite BIF (Fe2O3 / Fe3O4 mixed with SiO2)

AI-generated identification · may be incorrect

Hardness: 5-6 on Mohs scale; Color: Dark grey, steel black, to rusty brown with distinct layered banding; Luster: Metallic to sub-metallic; Crystal structure: Hexagonal/Trigonal (Hematite); Cleavage: None; Specific Gravity: 4.9-5.3.

Hardness: 5-6 on Mohs scale
Luster: Metallic to sub-metallic

Identified May 4, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in ancient oceans during the Precambrian era (approx. 2.4 to 1.8 billion years ago) through the precipitation of iron and silica from seawater as oxygen levels rose, known as the Great Oxidation Event.

Uses & applications

Primary source of iron ore for the production of steel worldwide. Occasionally used for decorative purposes or as geological educational specimens.

Geological facts

These rocks provide the primary evidence for the Great Oxidation Event, representing the transition when the Earth's atmosphere and oceans first began to accumulate free oxygen.

Field identification & locations

Identified by high density, distinct dark/reddish layers, and magnetic response if magnetite is present. Found in major deposits in Western Australia, Brazil, and the Lake Superior region of North America.