Lucara said the 1,111 carat precious stone was found at its Karowe mine in north-central Botswana, one of the world’s most prolific diamond-producing areas.
“It is almost impossible to estimate a value for such an extraordinary stone given that a valuation is highly dependent on the colour, clarity and cutting and polishing characteristics,” said Edward Sterck, a London-based analyst at BMO Capital Markets, Bloomberg news agency reports.
Gem Diamonds held the record for the largest discovery this century with the 603-carat Lesotho Promise, it reports.
The biggest diamond discovered is the 3,106-carat Cullinan, found in South Africa in 1905.
It was cut to form the Great Star of Africa and the Lesser Star of Africa, which are set in the Crown Jewels of Britain.