| 423 / | HD | CHEMISTRY OF INORGANIC COMPOUNDS |
| 324 | DF | SILICON OR COMPOUND THEREOF {4} |
| 325 | DF | .~ Oxygen containing {2} |
| 326 | DF | .~.~ Metal containing (i.e., silicate) {3} |
| 327.1 | | .~.~.~ Aluminum containing {2} |
| 327.2 | DF | .~.~.~.~> Mullite |
| 328.1 | DF | .~.~.~.~> Aluminosilicate {3} |