The purpose of the present investigation was to undertake a systematic study of cordierite compositions to determine to what extent the ultimate refractoriness and use temperature could be increased by the addition of zirconia without increasing the thermal expansion above 4.0 x 10⁻⁶ cm./cm./°c. A procedure has been presented for making the compound cordierite. Several raw batch compositions which can be expected to produce a high percentage of relatively pure cordierite on a one-fire basis are given. Data are presented tabulating the coefficients of thermal expansion of cordierite specimens containing increasing percentages of zirconia, the thermal shock resistance of these same specimens, the pyrometric cone equivalents of those specimens which possessed expansions lower than 4.0 x 10⁻⁶, and the effect of firing temperature on the absorption and distortion of a specimen possessing the maximum allowable thermal expansion. The results of the investigation indicate that zirconia does not materially extend the short firing range of cordierite compositions and the refractoriness of cordierite is not increased by the addition of zirconia at least in amounts up to 40%. It was found that a 70% cordierite-30% zirconia body could be used at a temperature of 1300°c without warping or undergoing shrinkage. / Master of Science