How to identify Turquoise with Matrix

To correctly identify Turquoise with Matrix (Turquoise (CuAl6(PO4)4(OH)8·4H2O) in host rock), 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

   Turquoise: Sky-blue, blue-green, apple-green. Matrix: Dark brown, black, reddish-brown, or tan.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Turquoise: Waxy to subvitreous. Matrix: Dull, earthy, or granular depending on the host rock.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Turquoise: Cryptocrystalline, massive, often reniform or botryoidal. Matrix: Variable, can be granular (sandstone), earthy (shale), or microcrystalline (chert). The overall texture is often a mosaic of turquoise and host rock.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Turquoise rarely forms macroscopic crystals; typically cryptocrystalline masses, nodules, or vein fillings. Matrix shows the texture of the host rock.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Turquoise: Perfect on {001} and good on {010}, but rarely observed due to cryptocrystalline nature. Matrix: Varies with host rock (e.g., shale may have platy cleavage, sandstone none).

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Secondary mineral in arid regions, forming in highly altered volcanic or sedimentary rocks, often associated with porphyry copper deposits. Found in veins, seams, and nodular masses within the host rock.

Key Facts

Hardness

5-6 (Mohs scale for turquoise component). Matrix hardness varies.

Specific Gravity

2.6-2.9 (for pure turquoise). The presence of matrix will slightly alter this value.

Crystal System

Triclinic (for turquoise).

Color

Sky-blue, blue-green, apple-green (turquoise); dark brown, black, reddish-brown (matrix).

Luster

Waxy to subvitreous (turquoise); dull, earthy, or granular (matrix).

Transparency

Opaque.

Fracture

Conchoidal to uneven (turquoise); variable for matrix.

Cleavage

Perfect on {001} and good on {010} (turquoise, rarely observed); variable for matrix.

Composition

Hydrous copper aluminum phosphate (CuAl6(PO4)4(OH)8·4H2O) for turquoise, embedded in various host rocks (e.g., limonite, chert, sandstone, shale).

Physical characteristics

• Crystal Habit: Cryptocrystalline masses, nodules, reniform, botryoidal, vein fillings. Matrix shows the habit of the host rock.
• Cleavage Type: Perfect {001}, good {010} (turquoise, rarely seen); variable for matrix.
• Fracture Type: Conchoidal to uneven (turquoise); variable for matrix.
• Tenacity: Brittle.
• Luster Type: Waxy to subvitreous (turquoise); dull to earthy (matrix).

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