How to identify Tiger's Eye

To correctly identify Tiger's Eye (Quartz (fibrous chalcedony with crocidolite inclusions)), 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. Hawk's Eye (blue Tiger's Eye) is blue-gray to blue-green.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Silky to vitreous, exhibiting strong chatoyancy.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Fine-grained, fibrous appearance due to the preserved crocidolite inclusions.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Massive, cryptocrystalline, typically found in veins or layers. Does not form macroscopic crystals.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None, due to its microcrystalline nature.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Occurs in metamorphosed banded iron formations, often in association with other quartz varieties, hematite, and magnetite. It forms in environments where silica-rich fluids can replace pre-existing crocidolite fibers.

Key Facts

Hardness

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

Specific Gravity

2.64-2.71

Crystal System

Trigonal (for quartz component)

Color

Golden-yellow, golden-brown, reddish-brown, blue-gray

Luster

Silky to vitreous, chatoyant

Transparency

Opaque to translucent

Fracture

Conchoidal to splintery

Cleavage

None

Composition

Silicon dioxide (SiO2) with fibrous inclusions of iron-rich amphibole (crocidolite)

Physical characteristics

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

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