THE world’s largest brilliant cut blue diamond is expected to fetch US$19 million when it goes to auction in Hong Kong on 7 October.
Named Premier Blue, the gemstone weighed in at 7.59 carats, and was the only one of its kind on record, graded as internally flawless by the Gemological Institute of America.
The button-sized carbon structure would be auctioned by New York-based auction house Sotheby’s, as a part of the company’s 40th anniversary sales in Asia.
The size, clear blue colouring, and round cut finish all reportedly contributed to Premier Blue’s value and aesthetic appeal.
The pigmentation in blue coloured diamonds is due to the presence of boron atoms; the higher the boron concentration, the deeper the colour. ‘Fancy vivid’, as was awarded to Premier Blue, is the grade for the highest saturation of colour.
The director of London-based jeweller Hancocks Guy Burton said the market for coloured diamonds was particularly competitive for investment purposes, or for use in high-end jewellery.
“Coloured diamonds have an obvious appeal: [their] market is strong because of their rarity,” Mr Burton said.
“People buy them for investment purposes, and they can be seen as a hedge against what happens in other markets.”
Coloured diamonds account for about 0.01 per cent of all mined diamonds, and are rarely finished into a brilliant cut, as this shape often wastes a large amount of the stone in the cutting process.
However, brilliant cut diamonds are most popular.
Earlier this year, Sotheby’s auctioned another large blue diamond, finished in an emerald cut. This 8.01 carat fancy vivid blue diamond sold for US$12.7 million.