| Solution | Length | |
|---|---|---|
| 4 letters | ||
| mohs | 4 | |
| 5 letters | ||
| rigor | 5 | |
| steel | 5 | |
| nails | 5 | |
| force | 5 | |
| 6 letters | ||
| temper | 6 | |
| 7 letters | ||
| granite | 7 | |
| stamina | 7 | |
| 8 letters | ||
| severity | 8 | |
| rigidity | 8 | |
| tenacity | 8 | |
| vitality | 8 | |
| strength | 8 | |
| solidity | 8 | |
| 9 letters | ||
| TOUGHNESS | 9 | |
| thickness | 9 | |
| stability | 9 | |
| stiffness | 9 | |
| roughness | 9 | |
| SOUNDNESS | 9 | |
| unfeeling | 9 | |
| viscosity | 9 | |
| 10 letters | ||
| sturdiness | 10 | |
| resistance | 10 | |
| profundity | 10 | |
| STRINGENCY | 10 | |
| 11 letters | ||
| vicissitude | 11 | |
| thick skin | 11 | |
| 12 letters | ||
| short shrift | 12 | |
| stubbornness | 12 | |
| RUTHLESSNESS | 12 | |
| 14 letters | ||
| relentlessness | 14 | |
| 16 letters | ||
| SPECIFIC GRAVITY | 16 | |