How to identify Tiger's Eye

To correctly identify Tiger's Eye (Tiger's Eye (a variety of Chalcedony, SiO2)), 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 oxides.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Silky to vitreous, exhibiting a distinct chatoyancy (cat's-eye effect) when polished.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Fine-grained, fibrous appearance internally, but smooth and polished externally for gemstones. Can feel cool and dense to the touch.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Massive, cryptocrystalline, typically occurring in veins. Does not form macroscopic crystals of its own, but rather pseudomorphs after fibrous crocidolite.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None. Exhibits a conchoidal to splintery fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Formed in hydrothermally altered metamorphic rocks, particularly those rich in crocidolite. Often found in banded iron formations or other silica-rich environments where amphiboles are present.

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 pseudomorphous after monoclinic crocidolite).

Color

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

Luster

Silky, chatoyant.

Transparency

Opaque to translucent.

Fracture

Conchoidal to splintery.

Cleavage

None.

Composition

Silicon dioxide (SiO2) with inclusions of iron oxides (goethite) and relict fibrous structures of crocidolite.

Physical characteristics

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

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