The demineralization of Thai, Colorado and Condor oil shales was carried out by three step treatment. The first step was decarbonation using HC1 aq., the second was demineralization using HF-HC1. At this stage, more than 10 wt.% of minerals based on products remained in the shales. It is considered that some kinds of minerals such as FeSx and fluoride salts remained judging from elementary analyses. The third step, washing by hot HC1 aq. was effective to remove these salts. The resulted shales contained 2.2, 2.5 and 2.7 wt.% of minerals based on the products, respectively.
Most of kerogen was recovered for Thai shale, while about 5% of kerogen lost for Condor shale. However, organic carbon recoveries were fairly good for every oil shales. This means that the kerogen content of Condor raw shale included not only kerogen but also some inorganic compounds which volatilize at the same temperature range as the kerogen does.
