Rare 20-carat blue diamond unveiled in Botswana Blue diamonds are very rare, comprising only about 0.02% of mined diamonds.

PRETORIA, South Africa -- Botswana unveiled the largest rare blue diamond ever discovered within its borders: a super rare "Fancy blue" diamond weighing more than 20 carats.

The unique gemstone was discovered at Botswana’s Orapa mine as a 41.11-carat rough stone. Its unusual and vibrant blue color is created by the molecular inclusion of the rare mineral boron -- which between one and three billion years ago was present in the rocks of ancient oceans during violent, diamond-forming volcanic activity.

“From the first moment we saw the diamond, it was clear we had something very special," said Marcus ter Haar, MD of Okavango Diamond Company. "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. It is incredibly unusual for a stone of this color and nature to have come from Botswana -– a once-in-lifetime find, which is about as rare as a star in the Milky Way,”

“It is little surprise blue diamonds are so sought after around the world as only a very small percentage of the world’s diamonds are classified as fancy color and, of those, only a select few can be classified as being Fancy Blue.”

The polished stone is named ‘The Okavango Blue’ in recognition of Botswana’s own environmental natural treasure and World Heritage site the Okavango Delta. It is further a symbol of Okavango Diamond Company, the diamond sales and marketing arm of the Botswana government.

Speaking to ABC News from Botswana, ter Haar said the diamond will not be put up for sale just yet.

“The iconic Okavango Blue will be showcased over the coming months to promote Botswana as a leading global producer of natural ethical diamonds with an anticipated sale toward the end of the year.”

“Only a handful of similar blue stones have come to market during the last decade, of which the Okavango Blue rightfully takes its place as one of the most significant,” said ter Haar.

Blue diamonds are so rare, they comprise only about 0.02% mined diamonds but their beauty and value is such that they include some of the world’s most famous jewels.

Diamonds are a key natural resource for Botswana and account for approximately half of government revenue.

The Gemological Institute of America has graded the stone as Oval Brilliant Cut, 20.46 carats, Fancy Deep Blue color, VVS2 clarity.