Mineral identification in Colombian coals using Mossbauer spectroscopy andX-ray diffraction

Minerals were identified in three Colombian coal samples from the Southwest of the country using Mossbauer spectroscopy and X-ray diffraction. Origina l and sink separated coal fractions of specific gravity 1.40 and 1.60 with particle size less than 600 mu m were used in the study. Using Mossbauer sp ectroscopy, the minerals identified in the original coal samples were pyrit e jarosite, ankerite, illite and ferrous sulfate, whereas by means of X-ray diffraction, minerals identified were kaolinite, quartz, pyrite, and jaros ite. Differences in mineral composition were found in the original and sink separated fractions using both techniques. Mossbauer spectra show that the mineral phases in low concentrations such as illite, ankerite and ferrous sulfate do not always appear in the spectra of sink coals, despite of those minerals occurring in the original coal, due to the fact that they are ass ociated with the organic matter and not liberated in the grinding process. X-ray results show that the peak intensity grows as the specific gravity is increased indicating that the density separation method could be an effect ive process to clean coal.