On researching this further on the internet there seem to be widely conflicting views on the subject. It's an interesting one though.
"http://www.newscientist.com/channel/earth/mg18624952.000" is an interesting read about the process in China and South Africa.
"http://www.newscientist.com/channel/earth/mg18624952.000" is an interesting read about the process in China and South Africa.
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