How to identify Turquoise

To correctly identify Turquoise (CuAl6(PO4)4(OH)8·4H2O), 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

   Sky-blue, robin's egg blue, greenish-blue, apple-green. The most prized color is an intense, uniform sky-blue.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Waxy to subvitreous, dull in massive forms.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically cryptocrystalline, massive, reniform, botryoidal, or stalactitic. Individual crystals are rare and microscopic.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Usually massive, nodular, or as vein fillings. Microscopic triclinic crystals are extremely rare.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None observed in massive forms due to its cryptocrystalline nature. Microscopic crystals show perfect {001} cleavage.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in arid regions, typically in highly weathered, altered volcanic or sedimentary rocks (e.g., porphyries, sandstones, shales) that contain copper, aluminum, and phosphorus. Often associated with limonite, kaolinite, chalcedony, and quartz.

Key Facts

Hardness

5-6 (Mohs scale)

Specific Gravity

2.60-2.90 g/cm³

Crystal System

Triclinic

Color

Sky-blue, robin's egg blue, greenish-blue, apple-green

Luster

Waxy to subvitreous, dull

Transparency

Opaque

Fracture

Conchoidal to uneven

Cleavage

Perfect {001} (rarely observed due to cryptocrystalline nature)

Composition

Hydrous copper aluminum phosphate

Physical characteristics

• Crystal Habit: Cryptocrystalline, massive, reniform, botryoidal, stalactitic, vein fillings, crusts. Individual crystals are microscopic and extremely rare.
• Cleavage Type: Perfect on {001} (only visible in rare, microscopic crystals). Typically appears to have no cleavage in hand specimens.
• Fracture Type: Conchoidal to uneven, splintery.
• Tenacity: Brittle
• Luster Type: Waxy to subvitreous, dull

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