How to identify Tiger Iron

To correctly identify Tiger Iron (Tiger Iron (a banded rock composed of Tiger's Eye, Red Jasper, and Hematite)), 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 golden-brown (Tiger's Eye), metallic gray/black (Hematite), and red (Jasper).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Varies from silky (Tiger's Eye) to metallic (Hematite) to dull/vitreous (Jasper).

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Fine-grained, compact, with visible banding. The Tiger's Eye component may show fibrous texture.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Not applicable as it is a rock composed of multiple minerals. Individual minerals within it have their own crystal forms (e.g., quartz in Tiger's Eye and Jasper is microcrystalline; hematite can be massive or platy).

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None for the rock as a whole. Individual mineral components have varying cleavage (e.g., quartz has no cleavage, hematite has no true cleavage but parting).

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Ancient marine sedimentary basins where banded iron formations (BIFs) were deposited, subsequently subjected to low-grade regional metamorphism and hydrothermal alteration.

Key Facts

Hardness

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

Specific Gravity

Approximately 3.3-4.0 (variable due to different mineral densities, hematite is denser).

Crystal System

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

Color

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

Luster

Silky (Tiger's Eye), metallic (Hematite), dull to vitreous (Jasper).

Transparency

Opaque.

Fracture

Conchoidal to uneven.

Cleavage

None (for the rock). Quartz has no cleavage. Hematite has no true cleavage but parting on {0001} and {1011}.

Composition

A rock composed primarily of Quartz (SiO2) in the form of Tiger's Eye and Jasper, and Iron Oxide (Fe2O3) in the form of Hematite.

Physical characteristics

• Crystal Habit: Massive, banded. Individual minerals are microcrystalline (quartz) or massive/platy (hematite).
• Cleavage Type: None (for the rock).
• Fracture Type: Conchoidal to uneven.
• Tenacity: Brittle.
• Luster Type: Silky, metallic, dull to vitreous.

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