Argyle Diamond Mine, Western Australia

The signature stone of Rio Tinto's Diamond Mine in the East Kimberley is the beautiful, rare pink diamond. They cost 20 times the price of an equivalent white diamond.

They are the world's largest supplier of diamonds and produce 20 million carats every year and account for one-fifth of the world's natural diamond production. The majority of diamonds are sold as rough or uncut stones by Rio Tinto Diamonds' central sales and marketing office in Antwerp, Belgium and also at their office in Mumbai, India. The rare pink diamonds are sold to jewellery manufacturers, designers and up market retailers.

Edit 28 December 2012:  Rio Tinto intends to sell its Argyle diamond mine or float it on the stock exchange.  Rio put a collection of 'hero' diamonds up for private tender - 56 pink diamonds, including two extremely rare red diamonds and 19 separate lots of blue diamonds, only found in the East Kimberley mine.  The world's rarest diamonds were snapped up by anonymous Japanese, Chinese and Indian buyers.