The 4 Cs of Diamonds: A Buyer's Guide

The 4 Cs of Diamonds: A Buyer’s Guide
When purchasing a diamond, whether for investment or jewellery, the 4 Cs—Cut, Colour, Clarity, and Carat Weight—are the universal grading system used to assess quality and value. Developed by the Gemmological Institute of America (GIA), these factors determine a diamond’s beauty, rarity, and price.
1. Cut
The cut of a diamond refers to how well it has been shaped and faceted from its rough form. A well-cut diamond maximizes light reflection, creating brilliance (brightness), fire (colour dispersion), and scintillation (sparkle).
Cut Grades (GIA Standard)
  • Excellent – Maximum brilliance and fire; best choice.
  • Very Good – Slightly less brilliance but still stunning.
  • Good – Decent sparkle, often found in commercial jewellery.
  • Fair – Less light reflection; appears dull.
  • Poor – Minimal brilliance, often appears lifeless.
2. Colour
Diamond colour is graded from D (completely colourless) to Z (light yellow or brown). The less colour a diamond has, the more valuable it is.
Colour Grades
  • D-F (Colourless) – Extremely rare and valuable; no detectable colour.
  • G-J (Near Colourless) – Slight warmth, but still appears white in settings.
  • K-M (Faint Yellow) – Noticeable colour, often used in vintage jewellery.
  • N-Z (Light Yellow/Brown) – Lower in value, but can be a stylistic choice.
3. Clarity
Clarity refers to the presence of inclusions (internal flaws) and blemishes (surface flaws). The fewer inclusions, the rarer and more valuable the diamond.
Clarity Grades
  • FL (Flawless) – No inclusions or blemishes, extremely rare.
  • IF (Internally Flawless) – No internal flaws, but may have tiny surface blemishes.
  • VVS1-VVS2 (Very Very Slightly Included) – Tiny inclusions, difficult to see even under magnification.
  • VS1-VS2 (Very Slightly Included) – Minor inclusions, often invisible to the naked eye.
  • SI1-SI2 (Slightly Included) – Visible inclusions under magnification, sometimes noticeable to the naked eye.
  • I1-I3 (Included) – Obvious flaws that may affect durability and appearance.
4. Carat Weight
Carat weight measures a diamond’s weight, not size. Larger diamonds are rarer and more expensive, but two diamonds of the same carat weight can look different based on their cut.
Common Carat Sizes & Approximate Diameters
  • 0.50 ct – 5.0 mm
  • 1.00 ct – 6.5 mm (Classic solitaire size)
  • 1.50 ct – 7.4 mm
  • 2.00 ct – 8.2 mm
  • 3.00 ct – 9.3 mm
Additional Considerations When Buying Diamonds
Certification (GIA, AGS, IGI, HRD)
Always buy a diamond with a certification from a reputable grading lab, such as:
  • GIA (Gemmological Institute of America) – Most trusted & strictest grading.
  • AGS (American Gem Society) – High-quality grading standards.
  • IGI & HRD – Common in Europe and Asia but considered less strict than GIA.
Fluorescence – Does It Glow Under UV Light?
Some diamonds emit a bluish glow under UV light. While this can reduce price, in some cases, it makes slightly yellowish diamonds appear whiter.
Shape vs. Cut
  • Round Brilliant – Most sparkle; retains value best.
  • Oval, Cushion, Emerald, Pear, Marquise, Princess, Asscher – Unique alternatives with different brilliance and style.
 
The 4 Cs of Diamonds: A Buyer's Guide