Mining giant Rio Tinto has received clearance from the US Federal Trade Commission on the pending sale of its Jacobs Ranch coal mine to Arch Coal.The deal is expected to close within the next six weeks. Rio announced the $761m sale of Jacobs Ranch, which shipped 42.1 million tons of coal in 2008, back in March.Jacobs Ranch, 55 miles south of Gillette, Wyoming, had about 381 million tons of proven and probable reserves at the end of 2008.