sedimentary

Banded iron formation (iron-rich jasper/chert)

Banded iron formation, chiefly quartz (SiO₂) with hematite, magnetite, and/or goethite (Fe oxides/hydroxides)

AI-generated identification · may be incorrect

Typically very hard (Mohs 6.5–7), dense, with metallic to earthy luster; this specimen shows tan jasper/chert and dark metallic iron-oxide bands, irregular fracture, and no obvious cleavage. Brown-yellow tones commonly indicate limonite/goethite or weathered hematite.

Identified September 10, 2026More sedimentary →

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At a glance

Common name: Banded iron formation (iron-rich jasper/chert)
Scientific name: Banded iron formation, chiefly quartz (SiO₂) with hematite, magnetite, and/or goethite (Fe oxides/hydroxides)
Category: sedimentary
Identified: September 10, 2026
Method: Standard

AI Estimated Value

About $10–$75 for a common hand specimen; $100–$500+ for unusually colorful, polished, or strongly patterned 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 deposited in Precambrian oceans, roughly 3.8–1.8 billion years ago, when dissolved iron precipitated as oxides alongside silica; later compaction, lithification, deformation, and weathering produced the folded appearance.

Uses & applications

Used as a major iron ore where sufficiently iron-rich; attractive pieces are cut or polished for cabochons, slabs, bookends, and mineral collections.

Geological facts

Banded iron formations record the rise of atmospheric oxygen and are among Earth’s most important clues to early ocean chemistry.

Field identification & locations

Identify by alternating silica-rich and iron-rich layers, very high density, rusty weathering, and possible magnetism if magnetite is present; common in Western Australia, Brazil, India, South Africa, Minnesota, and Michigan.