chamotte

Century Dictionary and Cyclopedia

1. n. Fragments of already burnt fire-clay, as of the old saggars of a porcelain factory, ground to powder and used, in admixture with fresh fireclay, in making new vessels. The old material serves to diminish the shrinkage of the mixture in the burning.

Wiktionary

1. n. A ceramic raw material with a high percentage of silica and alumina.