| Answer | Crossword Clue |
|---|---|
| OPAL | Form of silica. |
| QUARTZ | Form of silica. |
| OPAL | Form of silica |
| FLINT | Form of silica |
| OPAL | Iridescent form of silica |
| OPAL | Morphous form of silica. |
| AGATE | Cryptocrystalline form of silica |
| OPAL | It's a form of hydrated silica |
| OPAL | Silica form. |
