November 2nd 2011

The total weight of all the diamonds in a piece of jewellery is one of the most frequently used selling points. However just a small variation in the details of some of those diamonds that make up the total diamond weight (TDW) can greatly affect the value of the piece of jewellery.

Generally speaking the depth of a princess cut diamond should be about 75% of its width. For example a princess cut diamond that had a depth that equalled 85% of its width would be a "fat" diamond and one that had a depth of 60% of its width would be a "skinny" diamond. 

The diamond in this old ring was a "fat" diamond. There are several reasons why a "fat" diamond is undesirable but the main reason is that the beauty of a diamond is seen from the top and if more weight is in the depth that leaves less displayed in its width.

I found a diamond to match the slightly rectangular shape of the existing one but this time with a correctly proportioned depth. It weighed .40cts, 11% less than the "fat" .45ct diamond but they both looked the same from the top. 

So lets look at the actual details of the "about" .50ct diamond of the old ring:

- weight .45ct
- slightly rectangular shape
- "fat" cut that gave it the width of a .40ct


Assuming that the colour and clarity of the diamonds are the same then the bottom line is that a .45ct slightly rectangular "fat" princess diamond is worth far less than a well cut/proportioned .50ct diamond. To me it is a stone I would reject.

In the finished ring above you can see that I have added 3 diamonds. I placed the slightly rectangular diamonds on either side of a pair of nicely matching (actually square) princess cut diamonds.  The customer has a new ring they love and now understands why the exact details of a diamond determine its value.

She also knows why one of the three diamonds I supplied was far cheaper than the other two and has made an informed purchase.