A monolithic refractory ceramic tube sheet for use in all-ceramic air-to-air indirect heat exchangers, the heat exchanger used in all temperature and all pressure applications. A method for forming the monolithic tube sheet includes casting a refractory ceramic in a mold, where portions of the mold comprise the housing of the heat exchanger. Precisely formed negatives are used to form through channels and vacancies within the tube sheet, which are precisely positioned within the mold allowing uniform and flush formation of openings which receive the ceramic tubes therein. The same mold is used to provide both tube sheets of a tube sheet pair allowing accurate alignment of tubes within the exchanger vessel resulting in ease of assembly and equal loading of tubes when in use.