Fine slag (FS) is byproduct of the coal gasification process, consisting of mineral-rich particles (MRP) and discrete residual carbon (DRC). MRP were separated using froth flotation method from FS and the ash content of separated MRP was higher than 98%. MRP were sieved into five sized fractions and its properties were studied by SEM/EDS, XPS, XRD, FT-IR and Raman spectroscopy. The results show that MRP are heterogeneous material which contain not only minerals but also residual carbon. The minerals in MRP contain most amorphous glass, together with minor proportions of crystal quartz. The MRP mainly consist of aluminosilicate and smallest (0-23 mm) particles have the most of aluminosilicate. Except for discrete residual carbon particles, there are also another two types of residual carbon within MRP. The first is embedded in the MRP matrix. The second is associated in chemical and/or physical way with the inorganic matter within MRP matrix. Residual carbon within MRP has a low degree of crystalline order. The main functional groups of residual carbon within MRP matrix are C-C, C-H and C-O. C-O which chemically bound with inorganic elements in the MRP forming C-O-M (M represents inorganic elements existing in MRP) groups. (C) 2020 Published by Elsevier B.V. on behalf of The Society of Powder Technology Japan. All rights reserved.