Cutting the Blue Moon diamond

Suzette Gomes, CEO of Cora International, with the Blue Moon diamond on exhibit at the Museum of Natural History of Los Angeles County. Photo by E. Chamorro for NHMLA.

Did you check the Blue Moon diamond on display at Natural History Museum of Los Angeles County? You will see that we added the resin models of the different steps of the cutting process. Thanks to information provided by Cora International and the master cutter, here is the description our volunteer Brittany gathered. It is interesting to see the process of having an extremely valuable rough blue diamond and making a decision on how to cut it to yield the best color, clarity and shape. Enjoy!

The added resin models on display at the Natural History Museum of Los Angeles County. Photo by E. Gaillou for NHMLA.

The Blue Moon Diamond is one of the rarest diamonds in the world. Therefore the cutting process is a rather meticulous procedure. The rough diamond must first be placed into the hands of a master cutter. Most master cutters have been working in the trade for decades. The master cutter will examine the natural growth features of the rough diamond. From there, many models of the stone will be made. Creating models at every stage is a very important and significant part of the cutting process. These models give a blueprint to follow in creating this beautiful and extremely rare gem. Each model will be marked to determine the best shape and size of the stone. Once the model is marked, the cutter will begin to form facets into the model on the cutting wheel. 

Zoom in on the models. The numbers you read represent the carat weight of some steps of the cutting process.Photo by E. Gaillou for NHMLA.

The first two models created, weighing 22.79 cts, help determine the shape that would give the highest yield in weight and to also achieve an “Internally Flawless” diamond grade. One model was created in to a “square cushion” shape and the other in to a “long cushion” shape.

The Blue Moon diamond at 22.79 carats. © Cora International.

Now at 19.30cts, it was determined that the “longer cushion” shape would give a slightly higher yield in weight and more assurance to achieve the “Internally Flawless” grade.

The Blue Moon diamond on the cutting wheel. © Cora International.

The Blue Moon diamond at 19.30 carats. © Cora International.

The Blue Moon diamond at 19.30 carats. © Cora International.

At 16.31 cts the crown facets were preliminary blocked in and prepared for the shaping process. The results are examined and the model begins to take shape. Another replica model was created with pavilion facets at 15.29cts. This model determined how the deep indented naturals would be removed while retaining optimal weight and achieving an “Internally Flawless” clarity.

Once 14.21cts were reached, it was known that the gem had now achieved the “Internally Flawless” clarity grade. After achieving the final result on the model, the rough diamond was then able to be faceted on the wheel and polished into one of the rarest and most exquisite diamonds in the world.

The Blue Moon diamond at 14.21 carats. One already can see the beauty of the stone! © Cora International.