sedimentary

Banded Iron Formation (BIF) / Jaspilite

Banded Iron Formation (predominantly Hematite, Magnetite, and Quartz/Jasper)

AI-generated identification · may be incorrect

Hardness: 5.5-7.0 (Mohs); Color: Alternating red/brown (jaspering) and silver/black/grey (iron oxides); Luster: Dull to sub-metallic; Structure: Finely laminated sedimentary layers; Cleavage: None.

Hardness: 5
Luster: Dull to sub-metallic

Identified July 2, 2026More sedimentary →

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Physical properties

Hardness: 5.5-7.0 (Mohs); Color: Alternating red/brown (jaspering) and silver/black/grey (iron oxides); Luster: Dull to sub-metallic; Structure: Finely laminated sedimentary layers; Cleavage: None.

Formation & geological history

Formed in marine environments during the Precambrian era (mostly 2.4 to 1.8 billion years ago) when oxygen produced by cyanobacteria reacted with dissolved iron in the oceans, causing it to precipitate out as minerals on the sea floor.

Uses & applications

Primary global source of iron ore for steel production; also used as semi-precious ornamental stone, paperweights, and lapidary specimens due to its striking patterns.

Geological facts

BIFs provide geological evidence for the 'Great Oxidation Event', representing a time when Earth's atmosphere first became enriched with oxygen. Huge deposits exist in the Hamersley Range (Australia) and the Lake Superior region (USA/Canada).

Field identification & locations

Identify by the distinct, rhythmic dark and light colored banding; the dark bands are often weakly magnetic. Commonly found in ancient cratons; collectors should look for high-contrast banding and lack of heavy weathering.