The Blue Moon Diamond

Last week I attended a GIA Alumni Lecture, The Tale of the Blue Moon Diamond. The lecture was presented by Alan Bronstein, a Colored Diamond Expert. Alan sets uncompromising standards for qualifying and sourcing the most rare and beautiful diamonds for discerning collectors and connoisseurs worldwide. With all the attention to Fancy Colored Diamonds earlier this year, I was excited to learn more about the Blue Moon Diamond.

Alan Bronstein

The Blue Moon Diamond is among the largest known Fancy Vivid blue diamonds ever found. Alan shared with us its history, from the moment the extraordinary rough diamond was discovered 3 years ago, and described the journey from rough diamond into one of the most magnificent and legendary diamonds of modern times.

Why is it called the Blue Moon Diamond?

The rough 29.6-carat Blue Moon Diamond

Although it is a Blue Diamond, the name is actually a tribute to its rarity – a reference to the expression ‘once in a blue moon.’ Aside from its sheer size, and remarkable clarity (less than 2% of stones are Flawless or Internally Flawless), another extremely rare and fascinating feature of this diamond is the highly unusual red phosphorescence, which can be observed when the stone is exposed to ultraviolet light. It is so exceptional that scientists from the Smithsonian Institution and the National Gem and Mineral Collection carried out extensive research on the diamond ahead of its exhibition & sale.

How Does a Blue Diamond Form?

Diamonds with a strong saturated color represent only a tiny percentage of all natural diamonds – and only a minute percentage of all natural color diamonds are blue. The blue arises from trace amounts of the element boron in the crystal structure. Less than one boron atom per million carbon atoms is sufficient to produce the blue coloration.

A Few Highlights About the Blue Moon

The Blue Moon Diamond drew widespread media attention when the discovery of the 29.62 ct rough at the Cullinan mine in South Africa was announced in January 2014. The Cullinan Mine is known for Fancy Blue Diamonds, including the Cullinan Dream and Oppenheimer Blue, two stones that received quite a bit of attention earlier this year.

In June 2014, after a few months of examination, the diamond was cut into a 12.03 ct cushion, graded by GIA as Fancy Vivid Blue and Internally Flawless.

The Blue Moon Diamond during cutting. © Cora International.

The Blue Moon made its first public appearance at the Natural History Museum of Los Angeles County on September 13, 2014 in a temporary exhibit.

The stone was purchased at auction by a billionaire tycoon as a gift for his daughter, at a record setting price of $48.5 million – more than $4 million per carat! That record was eclipsed when the Oppenheimer Blue sold in Geneva for $57 million earlier this year.