The 4Cs of Diamonds Explained: Cut, Colour, Clarity and Carat

Published: 2026-03-31 | Author: Benny Gabay

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Why the 4Cs Matter

The 4Cs - Cut, Colour, Clarity, and Carat - are the universal standard for evaluating diamond quality. Developed by the GIA (Gemological Institute of America), this system allows buyers to understand exactly what they are purchasing. Every certified diamond at Diagem is graded across all four criteria.

Cut: The Most Important C

Cut is widely considered the most important of the 4Cs because it determines how well a diamond reflects light - its brilliance, fire, and scintillation. Cut does not refer to the shape of the diamond, but to the quality of the craftsmanship: the proportions, symmetry, and polish.

GIA grades diamond cut on a scale from Excellent to Poor. At Diagem, we stock diamonds with a minimum cut grade of Excellent (EX), ensuring every stone delivers maximum brilliance.

• Excellent (EX) - Maximum brilliance and fire
• Very Good (VG) - High brilliance, minor compromises
• Good (GD) - Acceptable, but noticeably less sparkle

Colour: D to Z Scale

Diamond colour is graded on a scale from D (completely colourless) to Z (noticeable yellow or brown tint). Truly colourless diamonds are rare and command a premium. In practice, most buyers cannot detect the difference between D-F (colourless) and G-H (near-colourless) grades when set in jewellery.

• D-F - Colourless: the rarest and most valuable
• G-H - Near-colourless: excellent value, barely detectable difference
• I-J - Near-colourless: slight warmth, good value for larger stones

Diagem stocks diamonds from D to H, covering the premium and near-colourless ranges.

Clarity: Internal and External Characteristics

Clarity refers to the presence of inclusions (internal) and blemishes (external) within a diamond. The GIA clarity scale ranges from Flawless (FL) to Included (I3). Most inclusions are microscopic and invisible to the naked eye.

• FL / IF - Flawless / Internally Flawless: extremely rare
• VVS1 / VVS2 - Very Very Slightly Included: inclusions invisible even under 10x magnification
• VS1 / VS2 - Very Slightly Included: inclusions visible under magnification, not to the naked eye
• SI1 / SI2 - Slightly Included: inclusions visible under magnification, usually invisible in the face-up view

VS2 represents the sweet spot for most buyers - excellent clarity at a significantly lower price than VVS or Flawless grades.

Carat: Weight, Not Size

Carat refers to a diamond's weight, not its physical size. One carat equals 0.2 grams. Two diamonds of the same carat weight can appear different sizes depending on their cut and shape. A well-cut diamond will appear larger than a poorly-cut stone of the same weight.

Prices increase non-linearly with carat weight. A 2ct diamond costs significantly more than twice the price of a 1ct diamond of similar quality, because larger diamonds are proportionally rarer.

Balancing the 4Cs

Understanding the 4Cs allows you to make intelligent trade-offs. For example, choosing VS2 clarity over VVS2 (virtually no visible difference) frees up budget to invest in a better cut or larger carat weight. Our team at Diagem can help you find the optimal balance for your budget.

Browse our natural diamonds or lab-grown diamonds, or read our full Diamond Buying Guide.

For a full breakdown of current diamond prices in South Africa, see our Diamond Price Guide.