The twice-yearly precious jewel sales held at glitzy hotels overlooking lake Geneva have been raking in eye- watering sums in recent years and the demand for coloured diamonds remains strong.
Sotheby's has put a target price of USD 30 million on the "Raj Pink", which was discovered as a rough crystal in South Africa in 2015, before being refined by a master cutter.
That price would be far short of the record USD 71.2 million that the 59.6-carat "Pink Star" earned in April, the highest amount ever paid for any gemstone at auction.
"Only on the rarest occasions do diamonds with vibrant, shocking colour like the Raj Pink's emerge", the GIA said.
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The top price ever earned at auction in the Fancy Intense Pink category came in 2010, when "The Graff Pink" went for a USD 46.2 million.
Sotheby's will be looking to beat expectations for the Raj Pink, which Christie's failed to do at its sale in Geneva yesterday.
Christie's labelled that a world record for a gem of its kind, meaning it was the highest price ever earned at auction for a so-called D colour diamond.
But an industry expert said the price paid by the anonymous buyer fell short of expectations and may be a warning sign of a softening diamond market.
"I am disappointed that the Art of de Grisogono didn't sell for a more dazzling price" said Tobias Kormind, head of 77 Diamonds, a major European online diamond jeweller.