Grading a Diamond : The 4 C’s

Are you buying a diamond engagement ring? Learn the basics before you take the plunge.

The quality and value of a diamond is based on the four C’s:

  • Carat
  • Colour
  • Clarity
  • Cut

Carat is an ancient unit of mass, standardized at the beginning of the 20th century and used to measure the weight of a variety of precious stones. It is very important to remember the carat refers to the weight and not the face-up side of a diamond.  It is a common misconception that carat refers to size, as larger stones will typically weigh more. This is important as for instance 1.0 carat diamonds can substantially in their diameter or face up size. The higher the carat of stone the heavier the stone.

Colour is judged using the internationally accepted GIA scale. There is a broad spectrum of colour for white or colourless diamonds and the whiter or more colourless a diamond the more valuable the stone. Colour is graded from D to Z with D be the finest colourless grade and Z the most opaque and least valuable. To determine and analyse the colour, a diamond is placed on a piece of white paper next to a set of master stones that have already been colour graded by experts using a comparable approach. Truly colourless diamonds are incredibly rare.

Clarity relates to the size, number and placement of inclusions within a diamond. An inclusion is a naturally occurring internal characteristic or irregularity. Diamonds are graded at 10x magnification then compared to the internationally accepted GIA Clarity Scale. Colour is graded from FL (flawless) to I3 (included) Diamonds that are SI-1 (slight included) clarity grade and above will have inclusions that are invisible to the naked eye when viewed from the top.

Diamond cutters strive to cut diamonds to maximize their beauty. The quality of cut is an assessment of the proportion, symmetry and overall appearance of the diamond. Cut is extremely important but the most difficult of the four Cs to assess. Well cut diamonds maximize the reflectivity, brightness, fire and the sparkle of the diamond. You will often hear cut referring to the shape of the diamond, however when speaking of cut in relation to the 4 C’s this strictly refers to the quality of the cutter’s craft, symmetry and polish of the stone.

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