Argyle diamond mine at the Ekati mine, both in Canada. However, Argyle has two to four times the concentration of diamonds (ore grade) of these mines. This makes extraction economically feasible, as mine costs are mostly related to the amount of ore processed, not the amount of diamond extracted. In 2005, Rio Tinto was given the go-ahead to a future expansion project, moving it from an open pit to an underground mine. This plan was postponed; in September 2010 Rio Tinto announced fresh plans to develop an underground mine beneath the existing pit, increasing annual production to 9 million tonnes of ore. The
Letseng diamond mine diamond ever found. It is a type II D colour, with potential to yield a cut stone. Chief executive Clifford Elphick said: "Preliminary examination of this remarkable diamond indicates it will yield a record-breaking polished stone of the very best colour and clarity, and has no inclusions visible in its rough form." The discovery of two large rough white diamonds was announced in November 2010. They weighed 196ct and 184ct. In January 2018 Gem Diamonds announced the largest diamond yet discovered at Letseng,a Type IIa D color stone measured at 910 carats. Letseng diamond mine The Letseng diamond mine, found