How to identify Tiger Iron

To correctly identify Tiger Iron (Tiger Iron (a banded rock composed of hematite, red jasper, and tiger's eye)), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Distinctive banding of metallic silvery-black to reddish-brown (hematite), opaque brick-red (jasper), and golden-brown with a silky sheen (tiger's eye).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Varies within the rock: metallic (hematite), dull to vitreous (jasper), and silky to chatoyant (tiger's eye).

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Fine-grained to microcrystalline, with a characteristic banded or layered appearance. The tiger's eye component will show a fibrous texture when viewed closely.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Not applicable as a rock; individual mineral components are microcrystalline (jasper, tiger's eye) or massive/specular (hematite).

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None for the rock as a whole. Hematite has no cleavage, jasper and tiger's eye (quartz) have no cleavage but exhibit conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Ancient shallow marine basins where chemical precipitation of iron oxides and silica occurred, followed by low-grade regional metamorphism and metasomatic alteration of crocidolite to tiger's eye.

Key Facts

Hardness

6.5-7 on the Mohs scale (due to quartz and hematite components).

Specific Gravity

Approximately 3.3-4.0, varying with the proportion of hematite (higher density) to quartz (lower density).

Crystal System

Not applicable for the rock as a whole. Quartz is trigonal, Hematite is trigonal.

Color

Banded metallic silvery-black/reddish-brown, opaque red, and golden-brown.

Luster

Mixed: metallic, dull to vitreous, silky to chatoyant.

Transparency

Opaque.

Fracture

Conchoidal to uneven (due to quartz and hematite components).

Cleavage

None.

Composition

A composite rock primarily composed of hematite (Fe2O3), red jasper (microcrystalline SiO2 with Fe oxides), and tiger's eye (silicified fibrous crocidolite, SiO2 with Fe oxides).

Physical characteristics

• Crystal Habit: Massive, banded, microcrystalline.
• Cleavage Type: None.
• Fracture Type: Conchoidal to uneven.
• Tenacity: Brittle.
• Luster Type: Mixed: metallic, dull, vitreous, silky, chatoyant.

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