| Shale Type | Related to Hydraulic Fracking | MBT* (meq/100g) | Water Content (Wt%) | Clay Types |
| Soft | Ductile | 20 - 40 | 25 - 70 | smectite illite |
| Firm | Less Ductile | 10 - 20 | 15 - 25 | illite mixed layer |
| Hard | Less Brittle | 3 - 10 | 5 - 15 | illite possibly smectite |
| Brittle | Brittle | 0 - 3 | 2 - 5 | illite kaolinite chlorite |