| 501 / | HD | COMPOSITIONS: CERAMIC |
| 1 | DF | CERAMIC COMPOSITIONS {15} |
| 94 | DF | .~ Refractory {8} |
| 126 | DF | .~.~ Trivalent metal compound (e.g., iron oxide, chromium oxide, trivalent rare earth oxide, etc.) containing {2} |
| 127 | DF | .~.~.~ Aluminum compound (e.g., clay, aluminium oxide, etc.) {1} |
| 128 | DF | .~.~.~.~ And silicon compound other than clay {2} |
| 130 | | .~.~.~.~.~ And clay containing {1} |
| 131 | DF | .~.~.~.~.~.~> Less than 40 percent by weight clay |