| Description | RC (MPa) | Example |
| Very low | 1 to 25 | chalk, salt |
| Low | 25 to 50 | coal, limestone, schist |
| Average | 50 to 100 | sandstone, slate, claystone |
| High | 100 to 200 | marble, granite, gneiss |
| Very high | >200 | quartzite, Basalt |