How to identify Turquoise

To correctly identify Turquoise (Turquoise (hydrated copper aluminum phosphate)), 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 blue color is due to copper, while green hues are often caused by iron impurities or dehydration.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Waxy to subvitreous, sometimes dull or earthy.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically massive, cryptocrystalline, or microcrystalline. Can be botryoidal, reniform, or stalactitic. Often found as veinlets, nodules, or crusts.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Rarely forms distinct crystals; when it does, they are typically small, tabular to prismatic triclinic crystals. More commonly found as cryptocrystalline aggregates.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect on {001} and good on {010}, but rarely observed due to its cryptocrystalline nature. Fracture is typically conchoidal to uneven.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Forms in arid and semi-arid regions as a secondary mineral in the oxidized zones of copper deposits. It is found in fractures and cavities within highly altered igneous, metamorphic, or sedimentary rocks, particularly those rich in aluminum and phosphate. Common host rocks include limonite, sandstone, shale, and altered volcanic tuffs.

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, sometimes dull or earthy

Transparency

Opaque

Fracture

Conchoidal to uneven

Cleavage

Perfect on {001} and good on {010}, but rarely observed due to cryptocrystalline nature

Composition

Hydrated copper aluminum phosphate

Physical characteristics

• Crystal Habit: Typically cryptocrystalline to microcrystalline massive aggregates; botryoidal, reniform, stalactitic, encrusting, or as veinlets and nodules. Rarely as small, tabular to prismatic triclinic crystals.
• Cleavage Type: Perfect on {001} and good on {010}, but usually not visible in massive material.
• Fracture Type: Conchoidal to uneven.
• Tenacity: Brittle.
• Luster Type: Waxy to subvitreous, sometimes dull or earthy.

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