How to identify Tiger's Eye and Turquoise

To correctly identify Tiger's Eye and Turquoise (Tiger's Eye (fibrous chalcedony, a variety of quartz) and Turquoise (hydrated phosphate of copper and aluminium)), 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

   Tiger's Eye: Golden yellow, golden brown, reddish-brown, sometimes blue (Hawk's Eye). Turquoise: Sky blue, robin's egg blue, blue-green, apple green.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Tiger's Eye: Silky, vitreous. Turquoise: Waxy to subvitreous.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Tiger's Eye: Fibrous, often polished smooth. Turquoise: Cryptocrystalline, massive, often with a fine-grained texture.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Tiger's Eye: Pseudomorph after fibrous crocidolite, typically massive or in veins. Turquoise: Cryptocrystalline, massive, reniform, botryoidal, stalactitic, or as veinlets.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Tiger's Eye: None (due to cryptocrystalline quartz). Turquoise: Perfect on {001}, but rarely observed due to cryptocrystalline nature.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Tiger's Eye: Formed in metamorphosed iron formations, often associated with asbestos deposits. Turquoise: Secondary mineral in highly altered igneous (e.g., porphyry copper deposits) or metamorphic rocks, typically in arid or semi-arid regions, often in association with limonite, kaolinite, and other copper minerals.

Key Facts

Hardness

Tiger's Eye: 6.5-7 on Mohs scale. Turquoise: 5-6 on Mohs scale.

Specific Gravity

Tiger's Eye: 2.64-2.71. Turquoise: 2.60-2.90.

Crystal System

Tiger's Eye: Trigonal (cryptocrystalline quartz). Turquoise: Triclinic.

Color

Tiger's Eye: Golden yellow, golden brown, reddish-brown. Turquoise: Sky blue, robin's egg blue, blue-green, apple green.

Luster

Tiger's Eye: Silky, vitreous. Turquoise: Waxy to subvitreous.

Transparency

Tiger's Eye: Opaque to translucent. Turquoise: Opaque.

Fracture

Tiger's Eye: Splintery to conchoidal. Turquoise: Conchoidal to uneven.

Cleavage

Tiger's Eye: None. Turquoise: Perfect on {001}, but rarely observed.

Composition

Tiger's Eye: Silicon dioxide (SiO2) with fibrous inclusions of limonite and altered crocidolite. Turquoise: Hydrated copper aluminum phosphate (CuAl6(PO4)4(OH)8·4H2O).

Physical characteristics

• Crystal Habit: Tiger's Eye: Pseudomorph after fibrous crocidolite, massive. Turquoise: Cryptocrystalline, massive, reniform, botryoidal, stalactitic, veinlets.
• Cleavage Type: Tiger's Eye: None. Turquoise: Perfect on {001}, but typically not seen.
• Fracture Type: Tiger's Eye: Splintery to conchoidal. Turquoise: Conchoidal to uneven.
• Tenacity: Tiger's Eye: Brittle. Turquoise: Brittle.
• Luster Type: Tiger's Eye: Silky, vitreous. Turquoise: Waxy to subvitreous.

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