| Answer | Crossword Clue |
|---|---|
| QUARTZ | It's 7 on the Mohs scale of hardness |
| APATITE | It's 5 on the Mohs scale of hardness |
| TALC | It's 1 on the Mohs scale of hardness |
| TOPAZ | It's 8 on the Mohs scale of hardness |
| GARNET | It's 10 on the modified Mohs scale of hardness |
| TOPAZ | It's between quartz and sapphire on the Mohs scale of hardness |
