The term "Zimmi" yellow diamond is more of an insiders' term, used mostly by diamond manufacturers and dealers. It's like a code name. When they use it, they mean to say - "this is no ordinary canary yellow diamond, it's color saturation level doubles that of other vivid yellow diamonds, and thus should be priced much higher".
When it comes to fancy yellow diamonds, the market price scale is usually stable and easy to figure out. All one needs to do is visit 3-4 websites of fancy color diamond suppliers, and the numbers will usually look the same. However, since GIA does not have a higher intensity level than "fancy vivid", it makes it a bit difficult to explain to someone not in the know how why it should be priced so steeply.
The name "Zimmi" refers to a small town in the Pujehun district of Sierra Leone, located right in the middle of the "Moa" and "Mano" rivers' Delta.
This mining area has known to produce some of the world's most amazing canary yellow diamonds.
Scientifically speaking, most of these diamonds are of the pure type Ib form. What makes these found so rare is that due to natural heat and time processes, such as nitrogen impurities within the diamond's lattice are known to aggregate. This usually results in larger defects that are common in the lesser pure types of IaA and IaB diamonds. The scientists at GIA laboratory who conducted a recent examination are not sure exactly how the impurities in these Zimmi type Ib stones avoided the aforementioned process. It's quite mysterious and ads more aura to the discoveries of such diamonds in the region.
To learn more about the uniqueness of these yellow diamonds you can read this excellent article form the GIA encyclopedia.
The added value of the origin of these diamonds can be compared to those of precious gemstones such as Rubies and Emeralds. Burma "Pigeon Blood" Rubies are worth more than twice than Rubies of other origin and with natural Emeralds, it's the Colombian stones that are the top of the pyramid.
When it comes to pricing, there are Two recent examples of just how high a value do auction houses and collectors attribute to Zimmi yellow diamonds. The first is at last year's Charities Geneva auction, which was highlighted by the sale of this item-
If we subtract the white diamonds on both earrings and gold (about 180k total) we come to about $11.4M paid for this yellow Zimmi diamond pair!
That is $470,000 per carat! and these stones got an "orangy-yellow" grading from GIA (that sometimes happens with Zimmi stones) which
is even considered a bit inferior to a straight "vivid yellow" color.
Obviously, a pair is rarer than a single stone but that can clearly give you an idea of the enormous value these stones hold over "regular" vivid yellow diamonds. They are truly within the same category
as the rare blue and pink diamonds, you see breaking records in an auction in the past years.
Just for comparison, let's take the most famous "regular" vivid yellow diamond sold in the past few years, the 110ct "Sun drop" diamond - it was sold for $105,000 per carat only!
A more recent example is an extraordinary item sold at Christie's November 2016 auction in Geneva. The unique 10.30 ct Vivid Orangy Yellow internally flawless octagonal cut diamond. This rare diamond was estimated to sell between 2 million – 3 million USD or 194,000 to 291,000 USD per carat.
Want to see it's final selling price?
Enter Christie's auction results here.
These auctions can be helpful for investors that don't have enough data to evaluate the performance of "Zimmi" yellow diamonds as investment tools, as there are only but a few available ones for sale in the market.
We also appreciate these stones very much, that is why over the years we have went to great lengths to obtain the purest rough canary diamonds to produce a few significant polished stones- Among them a 9.51ct Emerald cut, a 5.49 round brilliant cut and the famous 10.95ct Asscher cut you can see in the video below. Find more of our Zimmi vivid yellow diamonds.
10.95 ct Asscher cut vivid yellow diamond from Reddiam on Vimeo.