Table 1: The chemical composition of shale samples.
| Oxides content | Shale (1) | Shale (2) | Shale (3) | Shale (4) |
| SiO2 | 51.8 | 54.3 | 55.7 | 51.4 |
| Al2O3 | 15.5 | 11.9 | 14.6 | 13.8 |
| Fe2O3 | 8.33 | 7.23 | 5.02 | 10.07 |
| CaO | 1.21 | 7.2 | 3.11 | 2.3 |
| Na2O | 1.1 | 0.61 | 1.3 | 0.98 |
| K2O | 2.2 | 1.14 | 3.24 | 1.25 |
| P2O5 | 0.25 | 0.23 | 0.15 | 0.49 |
| MnO | 0.68 | 0.37 | 0.47 | 0.09 |
| TiO2 | 1.27 | 0.81 | 0.97 | 1.22 |
| SO3 | 0.71 | 0.63 | 0.52 | 0.65 |
| MgO | 1.43 | 1.18 | 2.44 | 1.82 |
| L.O.I | 15.55 | 14.1 | 12.23 | 15.96 |