BHP Billiton, owner of the Ekati Mine in Canada’s Northwest Territories, has made an offer to acquire Rio Tinto, which owns Australia’s Argyle Mine and Zimbabwe’s Murowa Mine and sells diamonds from Diavik, the other mine in the Northwest Territories.

Rio has rebuffed the offer, calling it too low, but at press time BHP said it was lining up shareholder support and may try again.

Diamonds would not likely be a major part of the combined company’s business, but such a company would be a far bigger player in the diamond market, with an estimated 15 to 20 per-cent of the market by value, with a significant presence in high-end stones.

There was also speculation that Anglo American, which owns 45 percent of De Beers, might get involved in the bidding.