Pre-Auction Impressions: November 11th 2015, Sotheby’s Geneva

On November 11th, Sotheby’s will feature ‘The Blue Moon’, a 12.03 ct, cushion cut, Fancy Vivid Blue, IF diamond. Only once every three or four years do we see an important blue stone of this caliber at auction. The high estimate is $4.5 million per carat.

The stone is owned by a few international diamond companies based in New York, Israel and India. A small percentage is owned by Petra, proprietors of the famous Cullinan mine that unearthed this blue rough among other famous blue diamonds in the last century.

This diamond has a magnificent blue color at the darker end of the Vivid scale. The bottom pavilion has four large facets with very small “berlandere” facets for decoration, leaving the cutlet area with subtle glimmer. The stone was planned and polished in New York.

According to the Fancy Color Diamond Index, Vivid Blue diamonds showed price increases of up to 6% in the last quarter. Price increases for blue diamonds may be partly due to the ripple effect of the ‘Blue Moon’ sale, even though the stone has yet to be sold. Many blue diamond owners are anxious to see the results of this auction as it may determine the value of their blue diamond inventory.

The auction will also feature an 8.24 ct, pear-shaped, Fancy Vivid Purple-Pink, SI1 diamond.

Although there is a striking difference between the catalogue and the stone in real life, this nicely shaped diamond exhibits an extraordinary sweet bubblegum color with a strong purple presence. In most cases, an SI1 grade will not dramatically affect the price of such a rare stone, but this particular diamond has inclusions that become visible to the naked eye when taking a closer look. The new buyer should focus on other attributes of the stone, not its clarity.

Most sellers emphasize the fact that the stone is a Type IIa, a detail that always seems to impress many diamond industry professionals, auction houses and collectors. The Type IIa classification in white diamonds is considered a real virtue because it indicates the stone has no nitrogen in its molecule composition, allowing it to exhibit a superior D color. It also corresponds with historical stones unearthed from the Golconda mine in India, which adds a lot of romance to the story of the stone.

Type IIa is not a virtue in pink diamonds. There is a tendency for Type IIa pink stones to decrease their intensity once they are exposed to UV light, as halogen or blue fluorescent light slightly washes out the color.

The high estimate of the stone is $2,020,466 price per carat.

Price Realized: $1,682,834 pc