* Rare pink diamond stranded on auction block in Geneva
* Lots fail to meet secret reserve price set by sellers
* Laurence Graff buys diamond earrings, emerald necklace (Adds Sotheby's statement, names Graff as buyer in paragraphs 8 and 10)
By Stephanie Nebehay
GENEVA, Nov 15 (Reuters) - A large pink diamond, rare for its colour and clarity, was among several major jewels that failed to sell on Wednesday at Sotheby's auction in Geneva.
The 37.3-carat cushion-shaped stone, known as the "Raj Pink" and mounted on a ring, was billed as the star lot at Sotheby's semi-annual jewellery sale in the Swiss city. The pre-sale estimate for the diamond, found in South Africa in 2015, was $20 million to $30 million.
Bidding opened on it at 9.9 million Swiss francs ($10.02 million) and climbed to 14 million Swiss francs before stalling.
"It was not sold," David Bennett, worldwide chairman of Sotheby's international jewellery division who conducted the auction, told the crowded sale room. The "Raj Pink" was named by its current owner, who wished to remain anonymous, Sotheby's said. The name is based on the Sanskrit word for king.
Other major lots were left hanging, failing to meet the secret reserve price set by their sellers.
They included a blue diamond ring by jeweller Moussaieff with a last bid of 12.4 million Swiss francs and a pair of yellow diamonds that formerly belonged to the German princely family of Von Donnersmarck, which reached 7.8 million Swiss francs.
Only 303 of the 349 lots found new owners, according to Sotheby's figures. In all, the sale netted 77.9 million francs.
A Harry Winston fancy light pink diamond ring, described as an "absolutely sensationally beautiful stone" by Bennett, brought the strongest price of the night and set a world record for that category at auction, Sotheby's said.
It sold for 12.6 million Swiss francs to a telephone bidder who purchased it from a European noble family which owned the 1970 piece by the New York jeweller, Sotheby's said.
Graff Diamonds Ltd, founded by London luxury jeweller Laurence Graff, scooped up two lots - a pair of flawless diamond earrings for 2.4 million francs and a 19th-century emerald and diamond necklace and matching earrings for 1.63 million francs, Sotheby's said.
"Pieces must be exceptional to sell today at the same level as two years ago," Eric Valdieu, a Geneva-based jewellery dealer formerly of Christie's, told Reuters after the auction.
The "Raj Pink" was not an easy stone to sell, he said, adding: "It was a modern, recent stone and not a 10 out of 10 in terms of its colour and form. It had no history," Valdieu said.
Tobias Kormind, managing director of 77Diamonds.com, Europe's largest online diamond jeweller, said in a statement that Sotheby's sale did not bode well for prices: "I'm worried for the top end of the diamond market."
At rival Christie's on Tuesday night, an emerald and diamond necklace set with the largest flawless white diamond ever to come to auction sold for a world record 33.5 million Swiss francs ($34 million), the star lot at its Geneva sale. ($1 = 0.9877 Swiss francs) (Reporting by Stephanie Nebehay; Editing by Cynthia Osterman)