Rio Tinto Unveils ‘Impossibly Rare’ Diamond

Melbourne, Australia--Last year, Rio Tinto made an astounding discovery at its Argyle mine in Western Australia and never said a word about it. The diamond mining company unearthed a 9.17-carat piece of rough that yielded a stone Rio Tinto Diamonds’ Patrick Coppens describes as “impossibly rare”--a 2.83-carat fancy deep grayish blue violet diamond that it dubbed the “Argyle Violet.” It is the largest violet diamond ever recovered from the mine. And now it will embark on a world tour, of sorts,...