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
Ekati Diamond Mine 62-million-year-old kimberlite pipes (Creaser et al., 2004) of the Lac de Gras kimberlite field, most of which lie underneath shallow lakes. Between 1998 and 2009, the mine has produced 40 million carats () of diamonds out of six open pits. As the high grade ore close to surface was depleted, development was completed to access the ore utilizing underground methods. Currently, there is one underground operation (Koala) with open-cut mining occurring in Fox Pit. The mine's current annual production is estimated to be approximately 7.5 million carats () of diamonds. Ekati supplies rough diamonds to the global market through its