Abstract: The present invention is a heat treatment jig for use in the baking process, the frit seal process, and the evacuation process during the manufacture of cathode-ray tubes. It comprises a base and one or more support members formed from a novel material comprising mica, talc, orthoboric acid, boric acid anhydride, and zinc oxide molded under heat and pressure. This novel molded material is superior in its mechanical properties to the substances (asbestos tape, asbestos cement, or boron nitride) used for the support members of conventional heat treatment jigs. In addition, it does not pose a danger to health like asbestos products and it is far lower in cost than boron nitride.