The largest blue diamond ever discovered in Botswana — a brilliant 20.46-carat oval gem with Fancy Deep Blue color and VVS2 clarity — was unveiled last week by the state-run Okavango Diamond Company.

"It is incredibly unusual for a stone of this color and nature to have come from Botswana. [It's] a once-in-a-lifetime find," said Okavango's managing director Marcus ter Haar.

The gem, which was cut from a 41.11-carat rough diamond sourced at the Orapa mine, was named "The Okavango Blue" to honor the world heritage site known as the Okavango Delta. The lush delta is the home to hippos, elephants, crocodiles, lions, leopards, giraffes and rhinos.

Okavango Diamond Company will be promoting The Okavango Blue in the lead-up to its sale at the end of 2019. While the company did not reveal what The Okavango Blue might be worth, a similar diamond sold at a Christie's auction in 2016 may hold the answer.

The Cullinan Dream, a 24.18-carat intense blue diamond with a VS2 clarity rating, sold for $25.4 million at Christie's New York in June of 2016. Based on that performance, one might presume The Okavango Blue has the potential to yield about $1 million per carat.

“From the first moment we saw the diamond, it was clear we had something very special,” said the managing director. “Everyone who has viewed the 20-carat polished diamond has marveled at its unique coloration, which many see as unlike any blue stone they have seen before.”

Blue diamonds are extraordinarily rare, owing their color to trace amounts of boron in the diamond crystal lattice.

Despite its tiny size, Botswana is one of the world's leading producers of top-quality diamonds. Botswana's Karowe mine, for instance, was the source of the 1,109-carat Lesedi la Rona — the second-largest rough diamond ever discovered. Diamonds are Botswana's main source of income and account for about 80% of its exports. Okavango Diamond Company is responsible for marketing 15% of the country's diamond production.

"Consumers can purchase Botswana diamonds with a sense of pride knowing that these diamonds are improving the lives of the people of Botswana,” said Okavango chief financial officer Lipalesa Makepe.

Credits: Images courtesy of Okavango Diamond Company.