Tiger Iron Identification Guide

What Tiger Iron Looks Like

Tiger iron is a banded sedimentary rock from ancient banded iron formations. It combines three components in wavy, parallel layers: golden-brown chatoyant tiger's eye (silicified crocidolite), brick-red to maroon jasper (iron-stained chalcedony), and metallic silver-gray hematite (sometimes magnetite).

• Color: alternating gold, red, brown, and steely gray bands
• Luster: silky/chatoyant in the gold layers, dull-waxy in the jasper, metallic in the iron layers
• Transparency: opaque
• Form: massive, layered; takes a high polish that makes the gold bands flash

Step-by-Step Field ID Checklist

1. Look for the three-part banding — gold + red + metallic gray together is the signature.
2. Tilt the gold layers in light; a moving silky light band (chatoyancy) confirms tiger's eye.
3. Check weight in the hand — tiger iron feels noticeably heavy due to the iron content.
4. Test a metallic gray band with a magnet; magnetite-rich pieces tug, hematite-rich ones do not.
5. Scratch an unpolished edge to confirm overall hardness near quartz.

Key Diagnostic Tests

• Hardness: ~6.5–7 in the silica bands (scratches glass easily); hematite bands are softer (~5.5–6).
• Streak: rub a gray band on unglazed porcelain — rusty red to red-brown streak from the hematite is decisive.
• Density: elevated (roughly 3.0–3.4) because of iron oxides; heavier than plain agate or quartz.
• Fracture: conchoidal in silica zones; no cleavage.
• Magnetism: weak to moderate where magnetite is present.

Common Look-Alikes

• Tiger's eye (plain): all gold/brown, lacks the red jasper and gray iron bands.
• Hawk's eye: blue-gray chatoyance, no red jasper.
• Mahogany obsidian: glassy, no chatoyancy, lighter, red-brown swirls only.
• Banded iron formation / jaspilite: has the red jasper and gray hematite but lacks the silky gold tiger's eye layers.
• Pietersite: brecciated swirling chatoyance without the discrete flat red jasper bands.

The combination of a red streak plus chatoyant gold plus high weight separates tiger iron from all of these.

Where It Is Found

The classic source is the Hamersley Basin of Western Australia, where Precambrian banded iron formations were locally silicified. Smaller occurrences appear in South Africa. It is sold worldwide as a lapidary and ornamental stone.