sedimentary

Banded iron formation (iron-rich chert), possibly jasper

Banded iron formation; alternating microcrystalline quartz (SiO₂) and iron oxides/hydroxides (hematite, magnetite, goethite)

AI-generated identification · may be incorrect

Hardness about 6.5–7 for quartz and 5–6.5 for iron oxides; dark brown, black, gray, and rusty bands with earthy to slightly vitreous luster. Massive, fine-grained texture; may be weakly magnetic if magnetite is present.

Identified September 16, 2026More sedimentary →

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At a glance

Common name: Banded iron formation (iron-rich chert), possibly jasper
Scientific name: Banded iron formation; alternating microcrystalline quartz (SiO₂) and iron oxides/hydroxides (hematite, magnetite, goethite)
Category: sedimentary
Identified: September 16, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a common hand specimen; $30–$150+ for attractive polished or strongly banded pieces.

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 with silica in ancient oceans, commonly during the Precambrian roughly 3.8–1.8 billion years ago, then compacted and lithified. The specimen appears naturally weathered or possibly polished/wet.

Uses & applications

Major source of iron ore after enrichment; attractive pieces are used as lapidary material, bookends, cabochons, and display specimens.

Geological facts

Its banding records changing ocean chemistry and oxygenation, especially the rise of atmospheric oxygen. Red-brown coloration commonly reflects hematite or goethite weathering.

Field identification & locations

Identify by distinct iron-rich and silica-rich bands, very high density, and possible attraction to a magnet; streak testing and acid testing can help distinguish it from ordinary jasper. Common in the Lake Superior region, Western Australia, South Africa, India, and Brazil.