How to identify Diamond

To correctly identify Diamond (Carbon (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

   Colorless, yellow, brown, green, blue, pink, red, orange, black. The most common colors are colorless to light yellow/brown. Fancy colors are rare and highly valued.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Adamantine (brilliant, like a polished metal, but with a glassy appearance).

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth to slightly rough on unpolished surfaces, often exhibiting growth features like trigons (triangular etch pits) on octahedral faces.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Typically forms isometric crystals, most commonly octahedra, dodecahedra, and cubes, or combinations thereof. Macles (twinned crystals) are also common. Industrial diamonds can be anhedral (irregularly shaped).

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect octahedral cleavage in four directions {111}. This means it can be split along these planes, despite its extreme hardness.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

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

Key Facts

Hardness

10 (Mohs scale), the hardest known natural mineral.

Specific Gravity

3.50 - 3.53 g/cm³ (varies slightly with impurities).

Crystal System

Isometric (Cubic)

Color

Colorless, yellow, brown, green, blue, pink, red, orange, black. Most commonly colorless to light yellow/brown.

Luster

Adamantine

Transparency

Transparent to opaque (depending on quality and inclusions).

Fracture

Conchoidal to uneven.

Cleavage

Perfect octahedral {111} in four directions.

Composition

Pure Carbon (C)

Physical characteristics

• Crystal Habit: Octahedral, dodecahedral, cubic, or combinations; also macles (twinned crystals), bort (poorly crystallized or industrial grade), and carbonado (polycrystalline aggregates).
• Cleavage Type: Perfect, octahedral {111}.
• Fracture Type: Conchoidal to uneven.
• Tenacity: Brittle (despite extreme hardness, it can be fractured or cleaved by impact along cleavage planes).
• Luster Type: Adamantine.

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