Jeweller unveils world's largest square emerald cut diamond

A view of the 1,109-carat 'Lesedi la Rona' the largest gem-quality rough diamond to be discovered in over a century, which was cut to create the 302.37ct Graff Lesedi La Rona. Photo / Getty Images

A London-based luxury jeweller has unveiled what is said to be the world's largest square emerald cut diamond.

The Graff Lesedi La Rona weighs 302.37 carats and is the "largest, highest clarity, highest colour diamond ever graded by the GIA", (Gemological Institute of America) said Graff.

The gem has a top D colour grade, meaning it is colourless – a trait which makes a diamond more valuable.

A world first: presenting the 302.37ct Graff Lesedi La Rona, the largest highest colour, highest clarity diamond ever certified by the GIA, and the largest square emerald cut diamond in the world. #lesedilarona #grafflesedilarona #graffdiamonds pic.twitter.com/vURecHKVAv

— graffdiamonds (@GraffDiamonds) April 10, 2019

It was cut and polished with painstaking care over 18 months from the second-largest rough diamond ever found – the 1109 carat Lesedi La Rona, found in Botswana in 2015.

Graff chairman Laurence Graff said: "My love affair with diamonds is life-long and crafting the Graff Lesedi La Rona has been an honour.

"This diamond, our diamond, is beyond words.

"All our expertise, skill and accomplishment went into crafting this incredible diamond masterpiece, which is extraordinary in every way.

"The Graff Lesedi La Rona is an exceptional diamond with an exceptional cut and exceptional proportions, earning its place in history as the largest and finest of its kind in the world."

Some 66 'satellite' diamonds were also polished from the original rough stone, Graff added.

Lesedi La Rona means "Our Light" in Tswana, the main language of Botswana.