How to identify Yellow Turquoise

To correctly identify Yellow Turquoise (Turquoise (var. yellow)), 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

   Typically yellow-green to yellowish, often with dark brown, black, or grey matrix veining. The color is often uniform due to dyeing.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Waxy to dull, sometimes sub-vitreous. True turquoise has a waxy to sub-vitreous luster.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth to slightly granular, often with a fine-grained appearance. The matrix can create a rougher texture.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Massive, nodular, or botryoidal. Rarely forms distinct crystals. If it's Serpentine, it can be fibrous (chrysotile) or platy (antigorite, lizardite). If Howlite, it's typically nodular or massive.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None to poor. Serpentine can have one perfect cleavage (antigorite) or none (lizardite). Howlite has no cleavage.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   If true turquoise, it forms in arid regions as a secondary mineral in aluminum-rich igneous rocks that have been altered by phosphatic waters. If Serpentine, it forms from the hydrothermal alteration of ultramafic rocks. If Howlite, it forms in evaporite deposits.

Key Facts

Hardness

Varies widely depending on the actual mineral: Serpentine (2.5-5), Howlite (3.5), Jasper (6.5-7). True turquoise (5-6).

Specific Gravity

Varies widely: Serpentine (2.5-2.6), Howlite (2.53-2.59), Jasper (2.58-2.91). True turquoise (2.6-2.9).

Crystal System

Varies: Serpentine (monoclinic), Howlite (monoclinic), Jasper (trigonal/hexagonal - cryptocrystalline). True turquoise (triclinic).

Color

Yellow-green to yellowish, often with dark matrix.

Luster

Waxy to dull, sometimes sub-vitreous.

Transparency

Opaque.

Fracture

Conchoidal to uneven.

Cleavage

None to poor (Serpentine can have one perfect cleavage).

Composition

Varies widely: Serpentine (magnesium iron silicate hydroxide), Howlite (calcium borosilicate hydroxide), Jasper (silicon dioxide). True turquoise (hydrous copper aluminum phosphate).

Physical characteristics

• Crystal Habit: Massive, nodular, botryoidal. Rarely forms distinct crystals.
• Cleavage Type: None to poor. Serpentine can exhibit one perfect cleavage.
• Fracture Type: Conchoidal to uneven.
• Tenacity: Brittle.
• Luster Type: Waxy, dull, sub-vitreous.

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