The 1,111-carat Lucara diamond is to be sold at auction sometime in the first half of this year in its rough form.

That will mean quite the payday for Vancouver-based Lucara Diamond Corp., which mined the gem in Botswana.

E-mails are streaming in from collectors wanting to buy the stone, the second-largest gem quality diamond ever found, according to Lucara CEO William Lamb. There have been offers as high as $30 million.

"We will take the stone on a road show. The details around the road show are very secret because it is potentially the highest value item on the planet," Lamb said in an interview with CBC's The Exchange.

The stone measures 65 by 56 by 40 millimetres, about the size of a tennis ball. One carat is equal to a fifth of a gram, so Lucara's 1,111-carat diamond weighs 222 grams.  

Sotheby's will auction off the stone, targeting a group of ultra-high net worth individuals, diamond dealers and collectors who might be able to pay the price it will command.

The Lucara diamond is the biggest gem-quality diamond discovered since the famed Cullinan measuring more than 3,000 carats was found in South Africa in 1905. The Cullinan was subsequently cut into smaller pieces, with the two largest portions incorporated into Britain's Crown Jewels.

To be sold uncut 

Lamb said Lucara has decided to sell the stone in its rough form.

"Because of its historical significance, nobody can really say whether it's more valuable in the polished form or the rough form. There will be collectors who will look to own the world's largest uncut diamond," he said.

It's not the only large stone Lucara has found at its Karowe mine in Botswana. Another of 813 carats and a third of 374 carats came from the same vein.

The find is a result of new diamond mining technology which enables the mining company to recover stones before they are broken up in the mining process.

Lamb said he learned of the stones at 4 in the morning Vancouver time, from the mine manager.

"He said to me 'are you sitting down.' Then he said 'Congratulations Lucara is the first company in more than a 100 years to find a diamond more than 1,000 carats.'"