Blog, Buyer's Guide

Diamonds: Cut

Buyers Guide: Diamonds, Part 1, Cut | Vardy's Jewelers Bay Area


If sparkle factor is your main requirement when purchasing a diamond, you must take the cut into consideration. The cut of a diamond is, hands-down, the most important contributor to how well or how poorly it reflects light. Along with cut comes proportion. A diamond must be cut to an ideal depth if light is to reflect back out the top. If one is cut too shallow, it will lose light through the bottom of the gem; too deep, and the light will reflect out the side. Both of these circumstances are factors to avoid when shopping for diamonds whether they are in a ring, earrings, a necklace or a bracelet.

Understanding Light Performance

Light performance in a diamond is measured according to brilliance, fire, and scintillation when the diamond is held in both a tilted and fixed position:

  • Brilliance — Brilliance is the manner in which a diamond reflects bright, white light.
  • Fire — Fire refers to how well it reflects bright, colored light.
  • Scintillation — Sometimes called sparkle, is the way a diamond reacts to light while moving.

Various factors affect light performance in a diamond, including star facet length, lower girdle facet length, the angle of the crown, and the size of the table. These are all factors that are influenced by cut. The most fiery, brilliant diamonds feature the most masterful cuts. They offer the best proportions, polish, and symmetry.

Balancing Optimal Cut Against Maximum Yield

Cut grades are created by determining how big of a diamond a cutter wants to obtain from the rough diamond. If the cutter is more interested in producing a bigger diamond overall, he or she may produce a diamond that’s all steep grades and deep angles. While this diamond will be bigger, it will sell for less because it’s a lower grade cut and it won’t reflect light in an ideal manner. Alternatively, if the cutter is more concerned with producing a diamond that will sell for a higher value per carat, he or she will cut at ideal angles — wasting more of the rough diamond — and raising the cost.

Understanding Cut Grades

Cut grades for diamonds are measured on a scale that ranges from ideal to poor:

  • Ideal — An ideal diamond is cut using ideal proportions, angles, and symmetry. In creating it, the cutter will waste more of the rough diamond. In this grade of diamond cut, light will both enter and exit from the top.
  • Excellent — A diamond that features an excellent grade of cut allows most of the light to reflect out the top.
  • Very Good — These diamonds are not cut perfectly. They don’t offer optimum brilliance because a portion of the light exits the diamond either out the side or out the bottom. In a very good grade, however, most of the light reflects back in the correct manner.
  • Good — Good cuts feature less brilliance but still feature an attractive sparkle.
  • Fair — A fair grade diamond is one that may have been produced because the cutter was trying to waste less of the rough diamond. This grade dulls in comparison to higher grade cuts.
  • Poor — A diamond that features a poor grade cut has been cut either too shallow or too deep. The light exits the stone in the wrong directions, making it appear lifeless, dull, and flat.

In summary, understanding diamond cuts — how they’re graded and how they reflect light — will help you score the brilliant, dazzling diamond of your dreams.