sedimentary

Banded iron formation fragment

BIF: microcrystalline quartz (chert/jasper) with iron oxides and/or magnetite

AI-generated identification · may be incorrect

Dark gray-black, fine-grained, with rusty brown-gold iron-rich bands; typically dull to slightly waxy, hardness about 6.5–7, no visible cleavage, and specific gravity roughly 2.7–3.3. The angular specimen appears naturally layered and may be weakly magnetic if magnetite-rich.

Identified September 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Chemical sediment formed when ancient oceans precipitated silica and iron minerals, commonly during the Precambrian roughly 3.8–1.8 billion years ago; later lithified and metamorphosed to varying degrees.

Uses & applications

Used mainly as an iron ore when sufficiently magnetite- or hematite-rich, and as lapidary stone, ornamental material, and educational specimens. This piece has modest collector value.

Geological facts

Alternating silica and iron-oxide layers record changing oxygen conditions in early oceans and are closely associated with the rise of atmospheric oxygen.

Field identification & locations

Identify by its repeated thin dark and rusty bands, very fine texture, and possible magnetic response; common examples occur in Australia, Brazil, India, South Africa, Ukraine, and North America.