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The cut of a diamond not only refers to its shape but also how well the stone reflects light. Simply put, it's responsible for the quality and degree of a diamond's sparkle. The better the cut, the more scintillation the diamond will have.

     

Precise artistry and workmanship are required to cut a diamond so that its proportions, symmetry and polish return the maximum amount of light possible. For many people, this is the most important of the 4Cs because it determines the beauty of a diamond. Whereas two diamonds may have the same clarity, colour and carat weight, cut is what determines whether or not one is superior to the other.

The GIA Grading Scale for Diamond Cuts

The Gemmological Institute of America (GIA) has a cut grade that determines how well a diamond sparkles. It evaluates:

  • How the diamond appears when viewed face-up based on the attributes of brightness, fire and scintillation
  • How well the diamond was designed to ensure durability and optimal weight
  • The quality of the workmanship or craftsmanship that went into aligning and polishing the diamond’s facets

Diamond cut grades are assigned into the following categories:

  • Excellent (EX) - High brilliance, scintillation, and an even pattern of light and dark areas. Seeing as almost all of the incoming light is reflected through the table, the diamond radiates with magnificent sparkle.
  • Very Good (VG) - Also featuring high brilliance and scintillation but slightly darker in the centre or around the edges. To the naked eye, Very Good diamonds provide similar sparkle to those of Excellent grade.
  • Good (G) - Stones with this grade will be a bit darker or lacking in scintillation. Much of the light still reflects through the table to the viewer’s eye, meaning these diamonds provide superb value.
  • Fair (F) - Very little brilliance or scintillation, as light easily escapes through the bottom and sides of the diamond. They may still be a satisfactory choice for smaller carats or side stones.
  • Poor (P) - Poor proportions and show very little brilliance or scintillation. Entering light escapes from the sides and bottom of the diamond.
     

    How is Diamond Cut Measured? The GIA cut grade combines three different types of reflections:
  • Brilliance - The brightness created by the combination of white light reflections inside and on the surface of the stone. Well-cut diamonds are brighter than poorly fashioned ones, even if they’re of equivalent size, colour and clarity.
  • Fire -  The spread of white light which appears as flashes of all the colours of the spectrum. When you tilt a diamond under light, you should be able to see red, blue, yellow or orange flashes.
  • Scintillation - This takes both sparkle and pattern into consideration. Sparkle refers to the spots of light that flash when the diamond, you or the light source moves, while pattern is the relative size, arrangement and contrast of the diamond's bright and dark areas.

By studying how successfully a diamond interacts with light to create these desirable visual effects, a cutter can evaluate what the best cut for any given stone is.

Tips for Buying Diamonds with Cut in Mind

  • It is near impossible to see the difference between an Excellent and a Very Good cut diamond with the naked eye because the direction of light is the same in both cut gradings.
  • If you're on a budget, a Good cut diamond offers a superb-value alternative without major compromises or quality defects. However, be careful you are not on the "Deep" side because this means the diamond will look smaller than the actual carat weight.
  • Don't forget that diamond cut, and diamond shape, are not the same thing. Diamond cut assesses the light performance of a diamond and is based on its proportions, symmetry, and polish. Diamond shape refers to the outline of a diamond, the most popular of which is the round brilliant.
  • Don’t underestimate the importance of diamond cuts. A well cut 0.90ct diamond could have the same width and give out more brilliance than a poorly cut 1.00ct diamond.
  • Even if you know what a diamond’s cut grade is, this shouldn’t be a substitute for seeing the diamond itself in person. After all, two diamonds with the same grade may look and perform very differently, especially under varying light conditions.

 

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