sedimentary

Banded Iron Formation (BIF) / Red Jasper with Hematite

Ferruginous Chert (primarily Quartz [SiO2] and Hematite [Fe2O3])

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs); Color: deep red, black, and silver/grey; Luster: vitreous to sub-metallic; Crystal Structure: microcrystalline/cryptocrystalline; Dense and heavy due to iron content.

Hardness: 6
Color: deep red, black, and silver/grey
Luster: vitreous to sub-metallic

Identified June 20, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: deep red, black, and silver/grey; Luster: vitreous to sub-metallic; Crystal Structure: microcrystalline/cryptocrystalline; Dense and heavy due to iron content.

Formation & geological history

Formed in marine environments during the Precambrian era (approx. 2.4 to 1.8 billion years ago) through the precipitation of iron and silica as oxidation levels in the atmosphere changed due to photosynthesis by cyanobacteria.

Uses & applications

Major industrial source of iron ore globally; used as semi-precious gemstones in jewelry (Jasper/Hematite) and as decorative ornamental stones or paperweights for collectors.

Geological facts

These rocks represent the 'Great Oxygenation Event' in Earth's history, capturing the moment the atmosphere first became oxygen-rich. They are most commonly found in ancient cratons like the Canadian Shield or Western Australia.

Field identification & locations

Identify by alternating red and black layers, high density/weight, and its ability to scratch glass. Commonly found in Great Lakes regions (Minnesota/Michigan), Australia, Brazil, and South Africa.