Collie coal is the only coal being mined in Western Australia and plays an important role in supplying cheap energy to the State's energy mix. This study reports a systematic investigation into the occurrence and characteristics of the fine mineral matter in Collie coal that is crushed to the size of < 212 mu m and density separated. The results show that 94.1 wt% of the mineral matter in the whole Collie coal is present in the three density fractions of 1.2-1.4, 1.4-1.6 and >= 2.0, including 26.8 and 58.6 wt% as included mineral matter in two density fractions with specific gravities of 1.2-1.4 and 1.4-1.6, and 8.7 wt% as excluded mineral matter in the density fraction of >= 2.0. Further analysis of these key Collie coal density fractions using computer-controlled scanning electron microscopy (CCSEM) shows that 54.13 wt% of the total mineral matter in the whole Collie coal are fine mineral particles of sizes < 10 mu m. These included fine mineral particles (< 10 mu m) are distributed as 20%:80% in the two coal density fractions of 1.2-1.4 and 1.4-1.6, which contribute to 10.64 and 43.49 wt% of the total mineral matter in the whole coal, respectively. CCSEM analysis also shows that the key minerals in the fine mineral particles are quartz, kaolinite, K-, Ca-or Fe-Al silicates and pyrite-related minerals. However, large proportions of these included fine mineral particles have "unclassified" mineral phases. Such unclassified particles contribute to 43.88 and 36.84 wt% of the fine mineral particles with size < 10 mu m present in the coal density fractions of 1.2-1.4 and 1.4-1.6 (equivalent to 4.67 and 16.02 wt% of the total mineral matter in the whole coal), respectively. The chemistry data show that these individual fine mineral particles (< 10 mu m) contain mixed compositions of Si + Al, Fe + Ti and other elements such as Ca, K, S and P, suggesting that one single fine mineral particle contains multiple mineral phases.