How to identify Turquoise and Ruby

To correctly identify Turquoise and Ruby (Turquoise (CuAl6(PO4)4(OH)8·4H2O) and Ruby (Al2O3:Cr)), 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. Ruby: Red, purplish-red, orangey-red.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Turquoise: Waxy to subvitreous. Ruby: Adamantine to vitreous.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Turquoise: Typically massive, cryptocrystalline, often with a fine-grained, porous texture. Ruby: Crystalline, often prismatic or tabular, sometimes granular.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Turquoise: Rarely forms distinct crystals; usually massive, botryoidal, reniform, or stalactitic. Ruby: Hexagonal system, typically forming prismatic, tabular, or bipyramidal crystals. Often found as irregular grains or masses.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Turquoise: Perfect on {001} (rarely observed due to cryptocrystalline nature). Ruby: No true cleavage, but exhibits parting on {0001} and {1011} due to lamellar twinning.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Turquoise: Secondary mineral in weathered, aluminum-rich igneous rocks (e.g., porphyries, rhyolites) in arid regions, often associated with limonite, kaolinite, and chalcedony. Ruby: Metamorphic rocks (marble, gneiss, schist) and some igneous rocks (basalt, syenite) associated with other corundum varieties, spinel, garnet, and mica.

Key Facts

Hardness

Turquoise: 5-6 (Mohs); Ruby: 9 (Mohs)

Specific Gravity

Turquoise: 2.60-2.90; Ruby: 3.97-4.05

Crystal System

Turquoise: Triclinic; Ruby: Hexagonal (Trigonal)

Color

Turquoise: Sky-blue, blue-green, apple-green; Ruby: Red, purplish-red, orangey-red

Luster

Turquoise: Waxy to subvitreous; Ruby: Adamantine to vitreous

Transparency

Turquoise: Opaque, rarely semi-translucent; Ruby: Transparent to translucent

Fracture

Turquoise: Conchoidal to uneven; Ruby: Conchoidal to uneven

Cleavage

Turquoise: Perfect on {001} (rarely observed); Ruby: None, but parting on {0001} and {1011}

Composition

Turquoise: Hydrous copper aluminum phosphate; Ruby: Aluminum oxide with chromium impurity

Physical characteristics

• Crystal Habit: Turquoise: Massive, cryptocrystalline, botryoidal, reniform, stalactitic; rarely small, distinct crystals. Ruby: Prismatic, tabular, bipyramidal, rhombohedral; often granular or massive.
• Cleavage Type: Turquoise: Perfect on {001} (rarely seen); Ruby: None, but parting on {0001} and {1011}.
• Fracture Type: Turquoise: Conchoidal to uneven; Ruby: Conchoidal to uneven.
• Tenacity: Turquoise: Brittle; Ruby: Brittle.
• Luster Type: Turquoise: Waxy to subvitreous; Ruby: Adamantine to vitreous.

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