Fig. 8. Scanning electron micrographs of shale fragments from the silt fraction of high cation exchange capacity (CEC) to percent clay samples of lignite overburden. (a) Shale fragment following overnight shaking in sodium hexametaphosphate. (b) Shale fragment following overnight shaking in sodium hexametaphosphate. (c) Shale fragment following destruction of CaCO₃, organic C, Fe oxides, sonication, and shaking overnight in sodium hexametaphosphate. (d) Shale fragment following destruction of CaCO₃, organic C, Fe oxides, sonication, and shaking overnight in sodium hexametaphosphate.