Courtesy of Okavango Blue Company
Diamonds are rare gems, but Blue diamonds are rarer.
Blue diamonds are a type of diamond with properties like that of every other diamond except with the appearance of blue colour, which is due to the presence of boron in its lattice.
As at April 17, 2019, one of the top producers of diamonds, Botswana unveiled a 20.46-carat blue diamond - the largest the country has ever discovered - which was discovered by its state-owned firm, Okavango Diamond Company (ODC).
Diamonds are very costly because they are rare, but the true value of a blue diamond also lies in its clarity. The value of the 20.46-carat blue diamond named Okavango Blue might surpass the largest blue diamond - 45.52-carat Hope Diamond with value of about $350 million.
The Gemological Institute of America (GIA) graded the Okavango Blue as "Very, Very Slightly Included" or VVS2 meaning inclusions (internal imperfections) are difficult for a skilled grader to see under 10x magnification. In comparison, the Hope Diamond received a "Very Slightly Included," or VS1 meaning inclusions are minor and range from difficult to somewhat easy for a skilled grader to see under 10x magnification.
Source: http://www.cnn.com/style/article/botswana-okavango-blue-diamond-scli-intl/