1) The ground was stone-hard, making it difficult to dig a hole for the tree.

2) The chef's stone-hard breadsticks were impossible to break with just your hands.

3) His resolve was stone-hard, unwavering in the face of adversity.

4) The soldier's stone-hard armor protected him from the enemy's attacks.

5) The teacher's stare was stone-hard, silencing the rowdy students.

6) She clenched her fists, feeling her nails dig into the stone-hard skin of her palms.

7) The frozen lake was stone-hard, making it safe for ice skating.

8) The criminal's alibi was stone-hard, backed up by multiple witnesses.

9) The diamond was stone-hard, able to cut through any material.

10) The old man's heart was stone-hard, closed off to any emotional connection.