World's Largest Uncut Diamond up for Auction in London

— -- The world’s largest uncut diamond will go under the hammer today at Sotheby’s auction house in London, where it’s expected to fetch at least $70 million.

The 1,109-carat white diamond was unearthed in November by the Lucara Diamond Corp. in their Karowe mine in north-central Botswana. It’s the largest diamond to be recovered in the southern African nation and the biggest find ever in more than a century.

The tennis ball-sized stone, named the Lesedi la Rona, or “Our Light” in Setswana, is thought to be 3 billion years old.

The Canadian mining company is going against the grain by selling the colossal rough at a public auction, rather than inviting sealed bids from some wealthy dealers in the diamond industry. The Lesedi la Rona is second in its size only to the huge 3,016.75-carat Cullinan Diamond, which was mined in South Africa in 1905 and produced nine major diamonds that are part of the historic Crown Jewels of the United Kingdom, according to Sotheby's.

“The Lesedi la Rona is a unique and important discovery,” David Bennett, worldwide chairman of Sotheby’s Jewelry Division, told ABC News. “We therefore felt that offering Lesedi la Rona in a Sotheby’s auction was perhaps the best way to share it with the widest possible audience.”

Two independent reports commissioned by Sotheby’s state the Lesedi la Rona may have the potential to yield one of the largest top-quality diamonds that has ever been cut and polished. The Gemological Institute of America also stated the rarity and characteristics of the stone in a letter to Sotheby’s, which was published by the auction house.

“The 1,109 ct rough’s top color and transparency exemplify the ‘limpid’ appearance commonly associated with type IIa diamonds,” the California-based nonprofit gem research institute wrote, referring to a rare subgroup that comprises less than 2 percent of all gem diamonds. “Once polished or examined in more detail a final answer will become clear.”

Lucara sold a rough diamond weighing 813 carats in May for $63 million, setting a new record for a rough gem. But by putting the Lesedi la Rona up for sale publicly, Lucara CEO William Lamb said he hopes the diamond will sell to someone who will showcase it at a museum instead of a private collection.

“Nobody has ever done anything like this before,” Lamb told ABC News, describing his emotions before the historic sale. “It’s a mixture of anticipation, nervousness, excitement.”

The Lesedi la Rona auction comes on the heels of record sales of large cut diamonds on the block. A 15.38-carat pink cut diamond sold for a record price of $31.6 million at a Sotheby's auction in Geneva in May. A 14.62-carate diamond named the Oppenheimber blue, which was apparently the favorite of millionaire Philip Oppenheimer, whose family once owned De Beers mining firm, fetched a record $57.5 million at Christie's auction house a day later in Geneva.

Lucara estimates that 60 percent of the total sales value of the stone will flow back into the Botswanan economy, as the government receives its royalty and taxes.

Botswana didn’t discover its diamond wealth until a year after it gained independence from the British in 1966. Today, it’s the world’s largest diamond producer and relies heavily on those export earnings.

The lucrative industry helped quadruple income per person in just three decades, pushing Botswana from a low-income country to a mid-income one. In 2002, with the HIV/AIDS epidemic at its door, Botswana used that revenue to become the first country in Africa to offer life-saving anti-retroviral drugs and other medications to those who need them.

Still, the mining industry hasn’t curbed the country’s high unemployment rate, and there are concerns about what will happen to the Botswanan economy if the diamond mines run out.