Rio Tinto unearthed the 187.7 Carat, Foxfire Diamond in August 2015 at its Diavik Diamond Mine, which is located about 130 miles from the Arctic Circle in Canada’s Northwest Territories.
The stone took its name from the aboriginal description of the Northern Lights as resembling a “brush of undulating fox tails.”
The mine was not known for large diamonds like the Foxfire, but rather much smaller stones. The chances of a large diamond coming through the sorting system were believed to be so slim that all large stones were assumed to be kimberlite, thus filtered and crushed. The Foxfire diamond could have been crushed, but because of its somewhat elongated shape, it slipped through the sifting screen.
In June 2016, Deepak Sheth of Amadena Investments, who trades in historic or unique stones, purchased the uncut diamond at auction (the exact price has not been publicly disclosed) and then did an unusual thing. He allowed the Smithsonian's scientists to borrow it.
“In some way, it's like diamonds are like meteorites from deep in the earth,” Jeffrey Post says, curator of the National Gem and Mineral Collection at the Smithsonian's National Museum of Natural History.
In order to find out more about the Foxfire diamond's composition, Post exposed the uncut gemstone to different types of light and used a spectrograph to see how the various elements in the diamond were reflecting the light. A funny thing was discovered along the way.
“One of the interesting properties of this diamond is that if you go in a dark room and turn on a black light, it glows bright blue. It lights up the room,” Post says. “There are a number of diamonds that do this, but this does so quite a lot. This happens through trace amounts of nitrogen. By doing spectral analysis of that light, we can tell how much nitrogen might be there.”
It gets weirder. “What is unusual, is that when you turn the light off [the diamond] continues to glow. First a deep orange color and then it fades to a creamy white glow. So that phosphorescence can tell us something about how that diamond was formed. . . . It gives us this interesting insight into its history that we wouldn't get just by looking at it.”
After laborious analysis and studies, the result came into two magnificient Pear Shape diamond with respective weight of 37.87 carats and 36.80 carats that is set into a pair of earrings with two white diamonds of 1.53 carats and 1.51 carats, both white Pear Shape diamonds coming from the same 187.7 carats Rough diamond!
The pair of earring has been sold through Christies for 1,572,500 USD at its Magnificient Jewels Auction in New York, USA on 5 december 2018. During that auction, a rare Fancy Intense Pink heart modified brilliant-cut diamond of 15.56 carats Type IIa, has been sold for 9,537,500 USD.