| Clue | Length | Answer |
|---|---|---|
| hardness | 5 letters | rigor |
| hardness | 5 letters | force |
| hardness | 6 letters | temper |
| hardness | 7 letters | stamina |
| hardness | 8 letters | tenacity |
| hardness | 8 letters | strength |
| hardness | 8 letters | solidity |
| hardness | 8 letters | rigidity |
| hardness | 8 letters | vitality |
| hardness | 8 letters | severity |
| hardness | 9 letters | stability |
| hardness | 9 letters | roughness |
| hardness | 9 letters | soundness |
| hardness | 9 letters | stiffness |
| hardness | 9 letters | unfeeling |
| hardness | 9 letters | viscosity |
| hardness | 9 letters | thickness |
| hardness | 9 letters | toughness |
| hardness | 10 letters | resistance |
| hardness | 10 letters | profundity |
| hardness | 10 letters | stringency |
| hardness | 10 letters | sturdiness |
| hardness | 10 letters | thick-skin |
| hardness | 11 letters | vicissitude |
| hardness | 12 letters | short-shrift |
| hardness | 12 letters | stubbornness |
| hardness | 12 letters | ruthlessness |
| hardness | 14 letters | relentlessness |
| hardness | 16 letters | specific-gravity |
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