Mining major Rio Tinto has given the sack to 78 people working at its Argyle diamond mine, reports say. The company said that this move was in effect to further its approach to be focused on costs, increased efficiency and the transition to a fully underground mining operation, reports add. The company had announced that production at its Argyle mine was up 87 percent to 3.13 million carats in the second quarter of this year, with increased tonnes processed and higher grades at the mine, reports say.