How to identify Diamond

To correctly identify Diamond (C), 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 colorless, but can be yellow, brown, green, blue, pink, red, or black due to impurities or structural defects.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Adamantine (brilliant, like a diamond).

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth to slightly rough on natural crystal faces; fractured surfaces are conchoidal.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Cubic system, commonly found as octahedra, dodecahedra, cubes, or combinations thereof. Macles (twinned crystals) are also common.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect in four directions (octahedral), meaning it can be split along these planes, despite its extreme hardness.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Primarily found in kimberlite and lamproite pipes, which are volcanic conduits that bring diamonds from the mantle to the surface. Also found in alluvial (placer) deposits, where diamonds have been eroded from their primary sources and transported by rivers.

Key Facts

Hardness

10 (Mohs scale), the hardest natural mineral

Specific Gravity

3.50 - 3.53

Crystal System

Cubic (isometric)

Color

Colorless, yellow, brown, green, blue, pink, red, black

Luster

Adamantine

Transparency

Transparent to opaque

Fracture

Conchoidal to uneven

Cleavage

Perfect in four directions (octahedral)

Composition

Pure carbon (C)

Physical characteristics

• Crystal Habit: Octahedral, dodecahedral, cubic, or combinations; also macles (twinned crystals) and bort (poorly crystallized or industrial grade).
• Cleavage Type: Octahedral, perfect on {111} planes.
• Fracture Type: Conchoidal to uneven, brittle.
• Tenacity: Brittle, despite extreme hardness.
• Luster Type: Adamantine (diamond-like).

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