Botswana unveiled a super rare "Fancy Deep Blue" diamond weighing more than 20 carats Wednesday — the largest blue diamond discovery ever made in the country. The unique gemstone exceeds the clarity and purity its world-famous predecessor, the Hope Diamond.

According to a press release by government-owned Okavango Diamond Company, the stone's bright blue color was "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."

The oval-shaped diamond was discovered at Botswana's Orapa mine as a 41.11-carat rough stone. It was then cut and polished, retaining 20.46 carats.

The stone has been graded as an Oval Brilliant Cut, VVS2 clarity by the Gemological Institute of America. The Hope Diamond, which was originally mined in India but is now housed at the National Museum of Natural History, has a lower clarity rating of VS1, but a larger size at 45.5 carats.

Get Breaking News Delivered to Your Inbox

"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."