Rio Tinto Plc (NYSE:RIO) and Glencore Plc (OTC:GLCNF) are weighing a potential spin-off of coal assets. Despite initial optimism, coal remains one of the complex obstacles to combining two vastly different portfolios and investor bases under one roof. Thus, moving those assets in a separately listed Australian vehicle is one of the discussion points amidst a $200 billion merger. Multi-Billion SpinoffAccording to the Australian Financial Review, Glencore's coal operations make roughly 8% of the combined grou ...