sedimentary

Banded Iron Formation (BIF) / Ironstone Conglomerate

Ironstone (Hematite/Goethite rich sedimentary rock)

AI-generated identification · may be incorrect

Hardness: 5-6 (variable); Color: reddish-brown to dark gray; Luster: earthy to sub-metallic; Crystal Structure: microcrystalline/amorphous; Cleavage: none; Specific Gravity: high (feels heavy for its size).

Hardness: 5-6 (variable)
Color: reddish-brown to dark gray
Luster: earthy to sub-metallic

Identified June 2, 2026More sedimentary →

Explore Banded Iron Formation (BIF) / Ironstone Conglomerate in the encyclopedia →

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Physical properties

Formation & geological history

Formed in ancient sea floors through the precipitation of iron oxides (Hematite, Magnetite) and silica, often dating back 1.8 to 3.5 billion years during the Great Oxygenation Event.

Uses & applications

Primary source of iron ore globally for steel production. Small tumbled pieces are used in lapidary work or as collector specimens.

Geological facts

These rocks are some of the oldest evidence of life on Earth, as the iron was precipitated out of the ocean by the metabolic processes of early oxygen-producing cyanobacteria.

Field identification & locations

Identified in the field by its high density, brownish-red streak, and tendency to be found in ancient cratons. Locations include the Lake Superior region (USA), Western Australia, and Brazil.