The surface properties of fossil fuel show differences according to ranks and mineral matter content. The fossils that have high mineral matter content are treated with some applications before using. This is a kind of enrichment. This process is helpful to both economic and technological points of view. The mineral matter of fossil can be decreased by chemical demineralization. The main purpose of demineralization is to separate the mineral matter without changing the organic structure. In this study, demineralization was studied using different acids (HCl, H2SO4 and HNO3) at various concentrations. Maximum demineralization degree (approximately 40%) was found of asphaltite sample leaching with 5 and 10% HCl acids. FTIR and XRD were used to determine the functional groups of treated sample and the contents of ash, respectively.