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Crystal Clear – Shape (general)
Diamonds are polished into a variety of shapes. The choice of shape is mostly one of taste, best use of the pre-polished rough diamond, and, at times, color. Most call a diamond's shape "cut." However, since January 2006, the term “cut” has referred to the proportions of the diamond, its Cut Grade, and the term ”shape” has since been the term for the form or contour of diamonds.
Though it may seem straightforward, there are many aspects to a diamond's shape. So we will address this with an overview and in the following articles discuss each shape group separately.
The most common diamond shape is round, however there are many different diamond shapes, including some very unusual ones, many of which were developed in the past decade for marketing reasons. Thee proprietary cuts were created in an attempt at creating differentiation.
Diamond shapes are commonly divided into three groups – Rounds; Semi Rounds, which are also known as Fancy Shapes; and Square shape diamonds. Each group of shapes is polished from rough diamonds that have the most fitting model to start with. A fitting model is one that results in the least amount of loss of material during the polishing process, the best yield.
While certain shapes are polished from certain model rough diamonds for efficiency reasons, some shapes result in a greater loss of material, or a lower yield. Rounds are the most wasteful in terms of yield and are therefore generally the most expensive diamond shape in terms of weight.
Depending on the shape of the rough diamond, during the polishing process of round cuts, as little as 28% and as much as 50% of the material is lost. The wide range of yield is because of the different rough diamond shapes (models).
Diamonds of different shapes differ in value. One reason for the difference is closely tied to the amount of material lost during polishing. The lower the yield, the higher is the cost of the diamond.
Half rounds include Pears, Hearts, Ovals, Marquise and Cushions. They are less wasteful to polish than rounds. Because of this higher yield, they have a lower value per carat of about 40% less.
Square shapes – Princess, Asscher, and Radiant – are the most efficient from a polishing perspective, and therefore valued at about 45% below rounds. These differences are not static, and may change according to fashion, trends, demand or availability of rough.
Just as with Clarity, where a polisher may prefer to make a diamond a little smaller to get a better clarity diamond, a polisher may want to make a decision on shape on the basis of the resulting value.
As part of the Crystal Clear philosophy, we described in past articles how different characteristics impact a diamond’s value. With all else being equal, we saw that heavier diamonds have a higher value than smaller ones, a diamond with better clarity has a higher value and a diamond with a better cut has a higher value. In the article on white diamonds we saw that diamonds with less color have higher value, and that with fancy color diamonds, value rises as color becomes deeper and stronger. Here is a demonstration of how shape impacts value.
Based on an analysis of current prices in the market of 1 carat, D color, IF clarity diamonds, we found that rounds have the highest per carat value. In the following table you will see the result of this analysis. The value of rounds is noted as 100% with the value all other shapes noted as a percent compared to rounds.
Value by Shape of 1 carat, D/IF diamonds
Because we know that value changes with clarity and color, we performed the same test for 2 carat, F color, VS1 diamonds and for 4 carats, I color, SI1 clarity diamonds. The results are very similar to the test above, but with small variations.
Value by Shape of Diamonds
2ct F VS1
4ct I SI1
In the above table, we see that the value variation trend continues, but that the decrease in value is not as sharp. The reason is that the weight of the diamond plays a growing importance in the value of a diamond in the larger goods. When compared all together, the trend becomes clearer.
As the above graph shows, for the 1 carat goods, the drop in average value is dramatic for all shapes compared to rounds. For 2-carat goods, the drop is less dramatic and for the very rare and sought after 4 carat goods, the decline compared to rounds is not as dramatic.
As stated in past articles, the intention of this review is to highlight a number of issues relating to diamonds, their value and how to understand the differing values of diamonds that may seem identical but differ enough to impact their value. These concepts are important to keep in mind if considering diamonds as part of a wealth preservation belief or even as a gift.
The views expressed here are solely those of the author in his private capacity. No one should act upon any opinion or information in this website without consulting a professional qualified adviser.