A 118.2 carat white diamond is to auction at Sotheby's Hong Kong on October 7 with an estimate of $25-$30m.

The auction, titled Magnificent Jewels and Jadeite, features a number of pieces of huge value and rarity. The D colour, flawless stone is the largest of its type and condition to have ever come to auction.

Discovered in South Africa in 2011, the 299 carat rough diamond was painstakingly worked on over a period of many months in order to achieve a flawless finish.

'The stone is also absolutely faultless and unbelievably beautiful'

Only four diamonds over 100 carats have come to auction previously, making this a major event in the international jewellery calendar. The diamond is 16% larger than the most valuable of the four - the 101.73 carat Winston Legacy - which sold at Christie's Geneva for $26.7m earlier this year.

Quek Chin Yow, chairman of Sotheby's international jewellery department, said: "Apart from its stunning size of 118.28 carats, the stone is also absolutely faultless and unbelievably beautiful. It therefore is a fitting offering in celebration of Sotheby's 40th anniversary in Asia."

Hong Kong has seen a rise in high profile jewellery sales in recent years and this upcoming auction is testament to its importance in the international sales of rare stones.

The auction includes a flawless round blue diamond, offered with an estimate of $19m - the largest and most significant diamond of its class as graded by the Gemological institute of America.

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