How to identify Silicon Carbide

To correctly identify Silicon Carbide (SiC), 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

   Natural moissanite is typically dark green to black, but can also be colorless, yellow, or blue. Synthetic SiC can be colorless, green, blue, or black depending on impurities and manufacturing process.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Adamantine to sub-metallic, often with a brilliant, almost greasy sheen.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Crystalline, often with sharp edges in synthetic forms. Natural forms can be granular or platy.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Hexagonal (alpha-SiC) or cubic (beta-SiC). Crystals are often tabular, platy, or prismatic. Synthetic crystals can be well-formed, often as hexagonal plates.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Poor to indistinct on {0001} in hexagonal forms. Fracture is typically conchoidal to uneven.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Natural moissanite is found in kimberlites, lamproites, some ultramafic rocks, and as inclusions in diamonds. It is also found in meteorites and impactites. Synthetic SiC is an industrial product, not naturally occurring in significant quantities.

Key Facts

Hardness

9.25 on Mohs scale (second only to diamond)

Specific Gravity

3.21 g/cm

Crystal System

Hexagonal (alpha-SiC) or Cubic (beta-SiC)

Color

Colorless, green, blue, black, yellow

Luster

Adamantine to sub-metallic

Transparency

Transparent to opaque

Fracture

Conchoidal to uneven

Cleavage

Poor to indistinct on {0001}

Composition

Silicon Carbide (SiC)

Physical characteristics

• Crystal Habit: Tabular, platy, prismatic, granular, massive. Synthetic forms often as hexagonal plates.
• Cleavage Type: Poor to indistinct, typically not observed in hand specimens.
• Fracture Type: Conchoidal to uneven, brittle.
• Tenacity: Brittle
• Luster Type: Adamantine to sub-metallic, sometimes greasy.

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