The Okavango Blue, is a 20.46-carat fancy deep blue diamond is on public display at the American Museum of Natural History in New York for the first time. Image: Okavango Diamond Company

The rare blue diamond is on loan from the Okavango Diamond Company and is the largest of its kind found in the Botswana. The GIA has graded it VVs1 in terms of clarity. Image: Okavango Diamond Company

The Okavango Blue Diamond is the centrepiece of a larger presentation about the variety of natural diamonds found in Botswana. Image: D. Finnin – American Museum of Natural History

Dr George E Harlow, American Museum of Natural History