Rio Tinto, the world’s No. 2 miner, has announced rejecting an informal takeover request from Swiss-based Glencore Plc, spurning a mega-deal that would have created a $160 billion mining and commodities trading giant. Rio Tinto announced, and Glencore representatives confirmed, a July phone inquiry; no further contact has ensued.

“The board, after consultation with advisers, concluded unanimously a combination was not in the best interests shareholders,” Rio Tinto said in an Australian stock exchange statement; Glencore CEO Ivan Glasenberg made the offer personally, according to a report by Reuters News.

Speculation over a Glencore bid for Rio Tinto had been brimming among analysts for weeks, fueled by a plunge in iron ore, which represents 90% of business for Rio, which has corporate London headquarters and management in Melbourne. Glencore’s $46 billion takeover of Xstrata last year was the biggest mining merger of its kind in recent history.

Iron would boost Glencore’s trading in copper, nickel, zinc and coal, while alleviating debt, according to observers. However, they added, significant hurdles include Rio Tinto shareholder dissent and a conservativeness contrasting with aggressive Glencore entrepreneurship, with Beijing’s Aluminum Corp. of China (Chinalco) 9.8% ownership compounding complexities.