sedimentary

Banded iron formation (iron-rich jasper/chert)

Banded iron formation, composed mainly of hematite–magnetite with microcrystalline quartz (jasper/chert)

AI-generated identification · may be incorrect

Hardness about 6.5–7 for quartz and 5–6.5 for hematite; reddish-brown, gray, black, and cream bands; vitreous to earthy luster; massive, fine-grained texture with no obvious cleavage. The rusty red areas are iron oxides, while pale bands are quartz-rich.

Identified September 17, 2026More sedimentary →

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At a glance

Common name: Banded iron formation (iron-rich jasper/chert)
Scientific name: Banded iron formation, composed mainly of hematite–magnetite with microcrystalline quartz (jasper/chert)
Category: sedimentary
Identified: September 17, 2026
Method: Standard

AI Estimated Value

Typically $10–$75 for a hand specimen; polished or unusually attractive specimens may sell for $100–$300.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Chemical sediment formed when dissolved iron precipitated from ancient oceans alongside silica, commonly around 2.5–1.8 billion years ago during periods of rising oxygen. The specimen appears weathered and fractured, with later oxidation producing its rusty colors.

Uses & applications

Important iron ore when sufficiently iron-rich; also used as decorative stone, lapidary material, and mineral-collection specimens. It is generally not used as gemstone-quality material unless polished.

Geological facts

Its alternating iron-oxide and silica layers record major changes in Earth’s ocean chemistry and atmospheric oxygen. Strongly magnetic pieces may contain abundant magnetite.

Field identification & locations

Identify by alternating red/black iron-rich and pale silica-rich layers, very high density, and possible attraction to a magnet; a red streak suggests hematite. Major occurrences include the Lake Superior region, Western Australia, Brazil, India, and South Africa.