Tuesday tips round-up: Rio Tinto, Intertek

It's cheap and dirty - coal, that is. It has also become increasingly less profitable as the price has continued to decline. Since spring 2011 it has nearly halved. In fact, in the case of Australian mining group Rio Tinto, and at the current market price of $62 a tonne, it is no longer profitable to dig up the stuff and transport it, analysts at BMO Capital have estimated.Broker Bernstein thinks Rio Tinto should spin-off the division, but instead the company has jumbled it together with its copper business. By doing so the miner may be attempting to keep its coal operations out of the view of investors, while it searches for potential buyers, yet there would seem to be little other reason to bring the units together and it is certainly not a long-term solution, says The Financial Times' Lex column.Some of the headwinds encountered by testing equipment manufacturer Intertek will abate over the coming year, but not all of them, so the shares are overvalued. Indonesia's ban on nickel exports in the first half of its last financial year added to the weakness in the minerals sector. The south east-Asian nation is the firm's largest client by volume. That will wash out this year. So too will the negative currency effects. Furthermore, the company is just about done exiting less profitable businesses.However, while the oil price has steadied of late, the headwinds in the oil and gas sector still look set to prevail. Meanwhile, the stock is trading on about 19 times' earnings forecasts and offers a dividend yield below 2%, not leaving much to go for. "Avoid for now," is the advice from The Times's Tempus.