| 501 / | HD | COMPOSITIONS: CERAMIC |
| 1 | DF | CERAMIC COMPOSITIONS {15} |
| 11 | DF | .~ Glass compositions, compositions containing glass other than those wherein glass is a bonding agent, or glass batch forming compositions {11} |
| 53 | DF | .~.~ Silica containing {3} |
| 55 | DF | .~.~.~ 40 percent - 90 percent by weight silica {7} |
| 65 | DF | .~.~.~.~ And boron {1} |
| 66 | | .~.~.~.~.~ And aluminum {1} |
| 67 | DF | .~.~.~.~.~.~> And zinc or zirconium |