When Glencore proposed a combination with Rio Tinto Group a decade ago, the larger company turned it down after just a few days. News this week that the two spent several months in negotiations in the second half of last year shows how the sands have shifted,

Rio Tinto (NYSE:RIO) and Glencore (OTCPK:GLCNF) (OTCPK:GLNCY) reportedly discussed a potential merger for months at the top level of both companies, in what would be the mining industry's largest-ever deal.

Glencore approached Rio Tinto late last year about combining the two big copper producers but the discussions are no longer active, a person familiar with the matter said. The talks between Rio, the world's No.