There are diamonds so rare that it is impossible to determine its value. The ‘Cora Sun-Drop’ is belonging to this category. It is one of the most stunning diamonds in the world.

Fantastic 110 carats, vivid bright yellow, the world’s largest known pear-shape diamond ‚Cora Sun-Drop’ goes on display in London. The brilliant ‘Sun-Drop’ will be on show from 25 February 2011 for up to 6 months at the world-renowned ‘Natural History Museum’ in London South Kensington. American model Jerry Hall, also known for her long-term relationship with Mick Jagger, was one of the lucky guests dazzled by the 110-carat ‘Cora Sun-Drop’ diamond when it was unveiled in the Museum’s Vault gallery.

The ‘Cora Sun-Drop’ has been lent to the museum by leading US diamond manufacturer Cora International New York. The Sun-Drop was mined in Africa. The diamond company crafted the original rough diamond. The strong yellow colour is a result of traces of nitrogen in the carbon structure of the diamond. Most diamonds are colourless - colours in diamonds are caused by the presence of structural defects or other substances.

Coloured diamonds are extremely rare in nature. Alan Hart, the Natural History Museum's minerals curator, told BBC News: 'I've never seen a stone such as this.’ And on the museum’s website Alan Hart is explaining in more detail: ‘Diamonds with a strong saturated colour represent only a tiny percentage of all natural diamonds, which makes them particularly interesting from a scientific perspective.’ and ‘In addition, extremely large diamonds (over 100 carats) with exceptional colours are historically significant as so few exist, so we are delighted to be able to show the Cora Sun-Drop to our visitors.’

The ‘Cora Sun-Drop’ diamond will be in good company. ‘The Vault’ is a permanent gallery at the ‘Natural History Museum’ dedicated to some of nature’s most rare, unique and valuable treasures. From the rare Martian meteorite ‘Nakhla’ and the Aurora Pyramid of Hope collection of 296 naturally coloured diamonds, each object in ‘The Vault’ has a story to tell, including the ‘Heron-Allen’s cursed amethyst’ and probably the world's most impressive crystallised 717 grams ‘Latrobe gold nugget’.

Cora International chief executive Suzette Gomes told BBC News the cut was vital in bringing out a diamond's beauty. Ms Gomes says the process is ‘like art… it takes a lot of courage and experience’. Ms Gomes also said, pricing stones was ‘not something we normally talk about,’ adding that ‘the value at the moment is undetermined’. Mr Hart outlined that, to the Museum, ‘the real value with these gems is that they're exceptional, they're one-offs’.