Rare earths content was tested using hydrofluoric acid, which is much stronger and more efficient than industrial methods, but is too hazardous to use on a large scale.
The figures demonstrate that developing nations in South East Asia require high quality coal to meet increased electricity demand, powered by the growing urbanization of the population.
Changes sweeping the electricity sectors in Japan and China suggest a hugely uncertain future for coal-fired power and a rapidly increasing risk of stranded assets.
Australia's Taurus raised $683m to invest in mining company debt last year, while two funds currently in the market are targeting investor capital of $800m.