How to identify Tiger's Eye

To correctly identify Tiger's Eye (Tiger's Eye (a variety of Chalcedony, which is a cryptocrystalline form of Quartz)), 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

   Golden-yellow, golden-brown, reddish-brown, sometimes with darker brown or black bands. The color is due to iron oxide inclusions.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Silky to vitreous, exhibiting strong chatoyancy (a moving band of reflected light).

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Fibrous appearance internally, but cryptocrystalline (microcrystalline) on a macroscopic scale. Smooth when polished.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Typically massive, occurring in veins or layers. Does not form macroscopic crystals of its own, but retains the fibrous structure of the original crocidolite.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None, due to its cryptocrystalline nature. Exhibits conchoidal to splintery fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in low-grade metamorphic terrains, often associated with serpentinite or other ultramafic rocks where crocidolite-rich veins have undergone silicification and oxidation.

Key Facts

Hardness

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

Specific Gravity

2.64-2.71 g/cm³.

Crystal System

Trigonal (as quartz, but cryptocrystalline).

Color

Golden-yellow, golden-brown, reddish-brown.

Luster

Silky to vitreous, chatoyant.

Transparency

Opaque to translucent.

Fracture

Conchoidal to splintery.

Cleavage

None.

Composition

Silicon dioxide (SiO₂) with inclusions of iron oxides (goethite).

Physical characteristics

• Crystal Habit: Massive, fibrous pseudomorphs after crocidolite.
• Cleavage Type: None.
• Fracture Type: Conchoidal to splintery.
• Tenacity: Brittle.
• Luster Type: Silky to vitreous, chatoyant.

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