This week I had an interesting experience evaluating a large diamond for a jewelry appraisal. A customer came to us from Guam to find out more about his mother’s diamond ring. According to his mom, the diamond was 3 or 4 carats. After evaluating the diamond, I was reminded about how little carat weight really means when talking about size. The round brilliant cut diamond in the ring had a diameter of 8.8mm, which is comparable to an excellent cut 2.75 carat stone and not a 3 carat diamond.
The jewelry trade uses “carat” to describe diamond weight, but this is all too often assumed to describe overall size. Although we would like to believe that all diamonds are cut perfectly, this is not the case. Diamond cutters have the pressure to meet certain bench mark weights that ultimately results in diamonds being cut deep to meet those “magic numbers”. In the case of this diamond, the weight very likely was 3 carats. However, the majority of that “size” is hidden in the pavilion. It is important when selecting a diamond that you understand how the weight is distributed within the diamond and ultimately if the stone is showing a competitive size.
Deep cut diamonds are abundant, but very shallow diamonds are as well. Shallow diamonds are diamonds that don’t have a lot of carat weight concentrated in the pavilion. Shallow diamonds can sometimes window (the eye can see past the bottom of the stone), but they also have the ability to show more size at a lower carat weight. I love to use my grandmother’s round brilliant diamond as an example. My grandmother received a 6.40 carat round brilliant cut diamond. The depth percentage is 57.4%, which is too shallow to receive an excellent cut grade by the GIA. This “Very Good” cut grade diamond does have one fantastic attribute with the diameter being 12.4mm, which is equivalent to a better proportioned 7 carat stone. Budget wise, this saved money and still got a very exciting overall size.
The moral of the story is that you always get what you pay for in the diamond business. A diamond priced surprisingly cheap most likely has a reason. The stone might be too deep or too shallow. Always ask to see the gemological certificate (if the stone is certified) and confide in a gemologist to get a professional opinion.