Why did you choose yellow diamonds to kick off the new online courses?
Yellow diamonds are some of the most prevalent fancy-color diamonds, and probably what most people understand as what fancy-color diamonds are. It seemed like a good entry point for the courses. And there are enough of them that people may have seen them before, whereas the other colors are so rare outside of champagne and brown diamonds. In terms of cost and price, it is a relatively entry-level color, not dissimilar from colorless diamonds.
What does the course cover?
The course is essentially anything you wanted to know about colored diamonds. It goes through how color is formed in diamonds, the history of yellow diamonds, where they come from, the different shades of colors, why they become these colors. It goes through the grading systems, which are not obvious in the way they work. And it goes through treatments, enhancement to colors and identification of that, and also synthetic yellow diamonds.
For whom is it designed?
When I put it together, what I had in mind was people working in stores, so they can understand what they are talking about when they talk to potential customers, but also the customers themselves, so they would learn from the bottom about colors and diamonds. The goal of the NCDIA [Natural Color Diamond Association] is to increase awareness of colored diamonds, and this dovetails very well with that.
When did yellow diamonds start being in demand?
I would say probably in the 1990s, when the explosion of fancy-color demand started. A lot of it had to do with the enhancements of the grading system that the GIA [Gemological Institute of America] put in place. So more and more of the colored diamonds were getting a report and getting out there to the trade. An understanding grew in the trade around colored diamonds and filtered to the public. Once people learned more about yellow diamonds and they became more prevalent in jewelry stores, people started asking about them and learning about them. As the information age grew, it was possible to learn about things and see images of them over the internet.
What’s different about yellow diamonds?
Once it gets to the point that the yellow is obvious, it’s clear it’s a whole different animal. As more people saw that and recognized that, the concept of it being like a defect or impure fell by the wayside, because they are beautiful, they aren’t defective.
Yellow is related to nitrogen, so instead of carbon, there is nitrogen. Many colorless diamonds have a lot of nitrogen. The only difference is the way it is arranged within the crystal lattice. Sometimes the nitrogen is aggregated or combined with other nitrogen in certain forms that don’t form any color. Sometimes it gets together and causes yellow. It is in no way a reflection of how much carbon or nitrogen there is in the stone, but [of] the way it is arranged. From a defect standpoint, there is no real relationship.
How easy is it to create lab-grown?
It is quite easy to create a lab-grown yellow diamond. The strongest yellow diamonds are ones where the nitrogen within the structure replaces a carbon atom. If you have a nitrogen instead of a carbon there, it causes a lot of light to be absorbed. It creates a stronger yellow color in the more common form. It is also the first way a nitrogen [atom] gets incorporated into a diamond — it takes the place of the carbon atom.
Up until 15 years ago, I would say the vast majority of synthetic diamonds were yellow, because it was very hard to control how much nitrogen was incorporated. It’s basically impossible to keep a diamond in such a way [and] at such temperatures and pressures that [the nitrogen atoms] would start to attach to each other, which is when the color diminishes. They learned how to keep them in that way now. Yellow synthetics were the most common type of synthetics up to 10, maybe 15, years ago. I spent a lot of time identifying them when I was at the GIA. It was part of my role. Yellow diamonds were subject to a lot of extra tests. They are pretty easy to pick up, but you definitely need to look for them.
How has the value of yellow diamonds evolved over time?
I would say 20 years ago, there was an increase after the GIA came up with the enhanced grading system — they added a new grade of vivid. Prior to that, it wasn’t agreed. It spurred more interest. It brought prices up. Since then, they’ve gone quite steadily upwards, and now they track not too far from colorless diamonds, I would think. I would not put them in the same category as pinks and blues, though.
Are yellow diamonds subject to a lot of treatments?
You can definitely treat diamonds to make them yellow, and it’s probably the most common treatment out there. One of the first tests in gemology to detect treatment was by G. Robert Crowningshield at the GIA, a very important figure in gemology. In the 1950s, there were a lot of yellow diamonds out there. He was able to study them after seeing thousands of samples, which is quite unheard in gemology. It was a seminal moment in the history of gemology.
Treatment doesn’t add value to the stone. It’s not compared in value to the natural ones. You definitely need a report from a reputable grading lab, especially [for] fancy color, as they can be quite tricky.
What’s the most outstanding yellow diamond you’ve ever seen?
The Sun-Drop diamond, a pear-shaped vivid yellow over 100 carats, has a very dramatic appearance.
And one I haven’t seen [is] the Eureka diamond that set off the diamond rush in South Africa in the 1860s. One of the reasons it was found in the first place is that it’s yellow, was sitting next to a river, and someone picked it up. It’s possible that color itself was one of the reasons diamonds were discovered at the time in South Africa.
The 30-minute NCDIA Yellow Diamond course is available at ncdia.com/education
Image: Rio DiamondsArticle from the Rapaport Magazine - September 2018. To subscribe click here.