Before we can talk about the issue of symmetry and girdle thickness, we first have to understand what makes up a diamond’s anatomy. The various parts of a diamond can be broken down into three main portions:
When you see a diamond that has a “very thin” or “extremely thin” girdle, you need to exercise extreme caution. Diamonds with very thin girdles are very susceptible to chipping during the setting process and normal daily wear.
In the example below, I had circled the portion of the diamond where the girdle thickness is going to be a major durability issue. To get a better idea of what I am talking about, do click on the corresponding links and view these diamonds under high magnification.
This particular diamond has an extremely thin – slightly thick girdle.
As I had mentioned before, the most vulnerable locations of a marquise diamond are found at its two pointed ends. In the following example, you can see that the girdle area at the tips are not thick enough to provide sufficient mechanical strength. A slight knock at the correct angle can cause significant damage and makes this diamond a very risky purchase.
The extremely thin girdle thickness at the tips makes this stone a poor choice.
Marquises have better spread and tend to look larger than other diamond shapes with similar carat weights. If you are a smart shopper and want to get more value out of your purchase, look out for diamonds with medium to slightly thick girdles. This will help you avoid diamonds that have excess weight “trapped” within the girdle area.
Why should you pay for “dead weight” that can’t be seen from a face up view?
To give you some perspectives on size and face up appearance, let’s take a look at the following diamonds:
#1: 0.81 Carat D Color VVS2 with a thin to slightly thick girdle. It measures up at 9.42 mm * 5.19 mm * 2.97 mm (L/W/D) and has a pretty decent face-up size for its carat weight.
#2: 0.82 Carat H Color SI2 with a uniform extremely thick girdle. In contrast, this diamond measures up at 8.94 mm * 4.61 mm * 3.22 mm.
Both diamonds weigh approximately the same but ironically, the 0.82 carat stone faces up significantly smaller even though it is heavier. Here’s another comparison of 2 stones with different girdle thicknesses.
– 0.46 Carat D Color SI2 with a medium to very thick girdle measures up at 7.98 mm * 4.18 mm * 2.48 mm
– 0.47 Carat D Color SI1 with an extremely thick girdle measures up at 6.83 mm * 4.00 mm * 2.65 mm
Again, the sizes differ significantly and the lighter diamond actually looks larger!
Now, please don’t misinterpret my intentions about maximizing spread to the extent that you start choosing diamonds with extremely or very thin girdles. A safe girdle thickness that would ensure better durability lies in the range of thin to very thick.
In my humble opinion, a diamond needs to be sparkly and be full of brilliance. However, a good diamond goes beyond that and only careful cutting can yield stones with character and enormous appeal.
By now, you should know that a marquise has the advantage of maximizes spread for its carat weight. However, this advantage comes at a price as marquises are very sensitive to symmetry details. As a result of poor cutting, a marquise can easily lose much of their wonders.
These images depict marquises with undesirable outlines and serve as a reminder to why shopping “blindly” is a bad idea. You need to understand that it is impossible to gauge the looks of a fancy shaped diamond based on its certification alone.
Sadly, I’ve seen it happened many times where eager shoppers buy solely based on a grading certificate (at sites like Bluenile.com) only to be disappointed with the outcome. It’s always a roll of the dice when you shop blindly and you won’t know what to expect until it is too late.
This ugly lop-sided marquise looks more like a pear.
Symmetry flaws are basically irregularities in the diamond’s cut and can occur as a result of many reasons. More notably, the presence of inclusions and the decision to remove them often lead to intentional symmetry flaws. Furthermore, cutters are under immense pressure to polish rough diamonds for maximum weight retention and often do it at the expense of cut.
Diamonds with poor symmetry usually exhibit a wavy girdle when viewed from its profile and these problems are so blatant they can be easily noticed by the unaided eye. The main concern with such symmetry flaws is that it makes the setting process very difficult and also causes the diamond to appear out-of-shape.
Notice how the red line I drawn to follow this diamond’s girdle isn’t straight? Avoid at all costs!