sedimentary

Banded iron formation pebble (likely jasper-rich ironstone)

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

AI-generated identification · may be incorrect

Dense, rounded, fine-grained pebble with muted red, gray, and greenish bands; submetallic to earthy luster, no visible crystals, and likely Mohs hardness about 6–7. Hematite gives red-brown tones, while magnetite may attract a strong magnet.

Identified September 1, 2026More sedimentary →

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At a glance

Common name: Banded iron formation pebble (likely jasper-rich ironstone)
Scientific name: Banded iron formation (BIF), composed mainly of hematite/magnetite and microcrystalline quartz (chert/jasper)
Category: sedimentary
Identified: September 1, 2026
Method: Standard

AI Estimated Value

About $3–$20 as a natural pebble; $20–$100+ if unusually attractive, polished, or clearly documented.

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 marine environments, commonly about 2.5–1.8 billion years ago, when oxygen produced by early organisms precipitated dissolved iron. Later compaction, silicification, and erosion produced this rounded cobble.

Uses & applications

Used as iron ore where sufficiently rich, aggregate, lapidary material, and collectible display stone; polished pieces are sometimes sold as “banded iron jasper.”

Geological facts

Classic BIF records Earth’s Great Oxidation Event and is especially abundant in ancient shield terrains. The apparent bands may be subtle where weathering or rounding has softened the contrast.

Field identification & locations

Look for alternating iron-rich red/black layers and pale silica, very high density, and possible magnetic response; a streak test gives hematite a red-brown streak. Common sources include Western Australia, Minnesota, Michigan, South Africa, India, and Brazil.