The world’s most precious diamond collection on sale

Global miner Rio Tinto (LON:RIO) announced Monday it is taking its collection of the world's most valuable and rare pink, red and blue diamonds on a global sale.

The rocks, mostly extracted from the miner's 27-year-old Argyle mine, which has practically produced the world's entire supply of rare pink diamonds, will be shown around the world for the next two months.

Manager of the collection, Josephine Johnson, said the diamonds were destined for investment portfolios or heirloom pieces of jewellery.

The collection includes 56 pink diamonds, two red diamonds and an additional 19 blue precious rocks.

The highlights are the Argyle Siren, a 1.32-carat square radiant cut pink diamond and the Argyle Satine, a 1.02-carat cushion cut pink diamond.

The biggest pink diamond ever found at Argyle was a 12.76-carat gem unveiled at the beginning of this year.

The Argyle Pink Diamonds Tender 2012 viewings will be held in Perth, Hong Kong and London with bids closing on October 15.

But not everything is shiny for Rio Tinto, as the world's third largest miner announced Tuesday  it is slashing staff at the Argyle mine to lower costs.