Golconda Type IIa diamonds, rare and glittering Featured

The Queen's personal collection is being exhibited at Buckingham Palace in summer 2012, including some of these beautiful stones

by 24 May 2012

Last December, the late Elizabeth Taylor's Krupp diamond (33.19 carat, D colour, VS1 clarity) was auctioned for an astonishing 8,800,000 USD. The diamond realized such a groundbreaking price not only due to its scale, but also because of its unique qualities. It is categorized as Type IIa, the value of which is 50 percent higher than other diamonds. The international standard for diamond evaluation is the 4C's (carat, clarity, colour and cut). Type IIa diamonds are in a league of their own.

In the photo below: the Gemological Institute of America is the authority that identifies Type IIa diamonds and certifies their value.

Less than 1% of the world's diamond production can be classified as Type IIa. The rarity and characteristics of these magnificent rocks make them exceptionally precious and much sought-after by the most discerning collectors. In recent years, Type IIa diamonds can only be acquired at international auctions. European royalty and collectors have long had a love affair with Type IIa diamonds, which have become noble family treasures that transcend time.

Gemological studies show that a combination of extremely high temperature and pressure contributes to a diamond's ultra-colourness and a high degree of transparency during its formation. Ancient literature used to describe Type IIa diamonds as 'the gem of the finest water' in reference to their crystalline clarity. They have a unique carbon molecule structure with a minute amount of nitrogen, the element that causes yellowness in diamonds. Some Type IIa diamonds are so bright that they seem to give off a bluish glow – identifiable with an ultra-violet light machine – in contrast to the fluorescence of ordinary diamonds.

You can see the 140.5-carat Regent diamond on Napoleon's coronation sword (on display at the Louvre Museum in Paris). This is a Type IIa diamond from India's Golconda region, which used to produce the most legendary diamonds up until the 18th century. While nowadays the legendary mines does not produce diamonds anymore, their legacy is such that very large diamonds extracted today - for example, from the mines of Brazil or South Africa - are also called named 'Golconda' diamonds.

In the photo below, at 110.57 carats, the Star of America is the world's largest Type IIa, D colour, flawless emerald-cut diamond, produced after eight months of cutting and polishing under Lawrence Graff's supervision.

Most Golconda diamonds belong to royal families, important museums or private collectors, but this does not mean that they have completely disappeared from the public eye. In fact, Elizabeth Taylor's Krupp diamond has brought the spotlight back onto to Type IIa Golconda diamonds. See them in a museum and you will no doubt gain a whole new perspective on collecting diamonds.

The show 'Diamonds: a Jubilee Celebration' is at the State Rooms of Buckingham Palace, 30 June-8 July, and 30 July-7 October 2012. It looks at the legacy of diamonds amongst the British monarchy over the past two hundred years, including some of the Queen's personal jewels.