The world's largest uncut diamond failed to sell at auction in London on Wednesday after the bids fell short of the reserve price.

The Lesedi La Rona, a 1,109-carat, tennis ball-sized gem found in Botswana, had been predicted to sell for over $70 million.

But the Sotheby's auctioneer failed to persuade bidders to go above $61 million for the jewel, which was discovered in 2015 by the Lucara Diamond Corp.

"Though widely admired in the months preceding this evening’s auction, and despite having seen bidding in the salesroom, the Lesedi la Rona failed to reach its reserve price and consequently did not find a buyer tonight," Sotheby's said in a later statement.

Sotheby's chairman of jewellery David Bennett had called the diamond "the find of a lifetime."

"No rough even remotely of this scale has ever been offered before at public auction," Bennett said ahead of the auction.

Precious stones have been fetching ever-higher prices at auction lately, as the world's ultra-rich invest in hard assets as a safeguard against stock market volatility.

Reacting to the failed sale, Tobias Kormind of 77 Diamonds online retailer said the bullish gem market "may have reached a tipping point and demand for large rare stones might just be saturated".

Alternatively, he said, "the market instability with Brexit may have just caused this to be a case of bad luck or bad timing."

Lesedi La Rona means "our light" in Botswana's Tswana language. It could be cut into smaller gems for jewellery or left whole in a private collection.

On the same day as the stone was discovered, another 830-carat diamond was found in Botswana, the third-largest in the world, William Lamb, Lucara's president and chief executive, told AFP.

The record for the biggest diamond in the world is still held by the "Cullinan Diamond", a legendary gem found in South Africa in 1905 boasting 3,016.75 carats.

The Cullinan Diamond was cut into nine diamonds for the British crown jewels.

They include the Cullinan I in the Queen's Sceptre and the Cullinan II, which is lodged in the crown that the British monarch wears to the opening of parliament.

A blue diamond from the same South African mine sold for over £25 million in New York this month.afp