metamorphic

Tiger iron slab (likely polished banded iron formation)

Banded iron formation (BIF), chiefly hematite/magnetite, quartz, and iron-rich amphibole or jasper

AI-generated identification · may be incorrect

Dark brown-black, subtly metallic to earthy luster with intricate red-brown and gray banding; hardness about 5.5–7, depending on quartz and iron minerals. The apparent curved bands are metamorphically folded layers, not crystal cleavage.

Identified August 14, 2026More metamorphic →

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At a glance

Common name: Tiger iron slab (likely polished banded iron formation)
Scientific name: Banded iron formation (BIF), chiefly hematite/magnetite, quartz, and iron-rich amphibole or jasper
Category: metamorphic
Identified: August 14, 2026
Method: Standard

AI Estimated Value

Approximately $20–$150 for a small/common slab; $150–$500+ for large, highly patterned polished material.

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

Formed from chemical sedimentary iron- and silica-rich deposits, commonly about 2.5–1.8 billion years old, then folded and metamorphosed. The specimen appears cut or polished, exposing the banded interior.

Uses & applications

Used for ornamental slabs, carvings, cabochons, and collector specimens; dense iron-rich varieties are less commonly used as ore than conventional BIF.

Geological facts

The pattern resembles tiger iron, a decorative variety of BIF often containing hematite, jasper, and chatoyant crocidolite or amphibole. Strong magnetism, if present, indicates abundant magnetite.

Field identification & locations

Identify by high density, alternating iron-rich and silica-rich bands, possible magnetism, and lack of vesicles; a streak test and magnet are useful. Classic tiger iron is associated with Western Australia, while BIF occurs worldwide.