How to identify Tiger Iron

To correctly identify Tiger Iron (Tiger Iron (a variety of Jasper, Hematite, 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 alternating bands of golden-brown (tiger's eye), metallic gray to black (hematite), and red to brown (jasper).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

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

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Banded, often with a fine-grained to microcrystalline texture. The tiger's eye component may show a fibrous texture.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

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

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None observed in the composite rock. Individual minerals have different cleavage properties (e.g., hematite has no true cleavage but parting).

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Formed within ancient banded iron formations (BIFs) that have undergone subsequent metasomatic alteration and low-grade metamorphism. Found in regions with extensive Precambrian shield rocks.

Key Facts

Hardness

6.5-7 on Mohs scale (due to quartz/jasper components), but can be slightly lower in hematite-rich areas (5-6)

Specific Gravity

Approximately 3.3-4.0 (variable due to different mineral densities; hematite is denser than quartz)

Crystal System

Not applicable as a composite rock. Quartz is trigonal, Hematite is trigonal.

Color

Banded golden-brown, metallic gray/black, red/brown

Luster

Mixed: silky/chatoyant, submetallic/metallic, dull/vitreous

Transparency

Opaque

Fracture

Conchoidal to uneven (due to quartz/jasper), splintery (due to fibrous tiger's eye)

Cleavage

None (in the composite rock)

Composition

A composite of microcrystalline quartz (jasper), fibrous quartz pseudomorph after crocidolite (tiger's eye), and iron oxide (hematite).

Physical characteristics

• Crystal Habit: Massive, banded, microcrystalline, fibrous (tiger's eye component)
• Cleavage Type: None
• Fracture Type: Conchoidal to uneven, splintery
• Tenacity: Brittle
• Luster Type: Mixed: silky, chatoyant, submetallic, metallic, dull, vitreous

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