NeerDoWellBlog: Blue Diamonds

All coloured diamonds contain interstitial impurities or structural defects that cause the colouration. Pure diamonds are transparent and colourless. Type IIa diamonds can be coloured pink, red, or brown due to structural anomalies caused through plastic deformation during crystal growth.

Type IIb diamonds, which account for 0.1% of gem diamonds, are usually light blue due to scattered boron within the crystal matrix; these diamonds are also semiconductors, unlike other diamond types. A blue-grey color may also occur in Type Ia diamonds and be unrelated to boron.

While extraordinarily rare, blue diamonds are not the rarest.

They are more uncommon than yellow diamonds, which have nitrogen in them, but they lose out in rarity to green, black, pink, orange, purple, and red.

The Hope Diamond is 45.52 carats and is the largest deep-blue diamond known. The stone can be traced to Golconda and is considered by many to be the most famous diamond in the world. Now on permanent display at the Smithsonian Natural History Museum in Washington, D.C. It is a Type IIb diamond and exhibits red phosphorescence after exposure to ultraviolet light.

The diamond is notorious for supposedly being cursed.

The Wittelsbach-Graff is a 31.06-carat, Fancy Deep Grayish Blue diamond with an IF clarity and an unusual cut with 82 facets. The stone sold in 2008 for $24.3 million.

On October 8th, 2007 a 6.04 carat Fancy Vivid Blue diamond set in a platinum ring, flanked by two white emerald-cut diamonds sold for $7.98 million at the Sotheby's Hong Kong auction.

This 7.03-carat blue diamond sold for $9 million at the Sotheby’s semi-annual sale in Geneva.

A recent find by Petra Diamonds. The 29.6-carat stone was recovered at its Cullinan mine, about 40km (25 miles) north-east of Pretoria.

Petra unearthed another 25.5 carat blue diamond which sold for $16.9m in 2013.

13.22 carat pear-shaped Fancy Vivid blue flawless diamond sold at Christie's Geneva on May 14, 2014 for $ 24m, setting a new world auction record for the price per carat for a blue diamond.

Immediately after the sale, it was renamed 'The Winston Blue'.

In the past decade, only three blue diamonds of 10 carats or more with the same vivid grading for intensity have been sold at auction, all weighing less than 12 carats and none flawless.

The Premier Blue is a 7.59-Carat Internally Flawless Fancy Vivid Blue Diamond.

Expected to bring upwards of $ 19m the stone did not find a buyer in late 2013.

A 6.01 carat Fancy Vivid Blue Diamond that sold for $10.1 million, or $1,686,505 per carat, at Sotheby’s Hong Kong in October 2011.

A 5.3 carat blue diamond fetched $9.6 million, or $1.8 million per carat in April 2013.