Porous zircon refractory brick were carbochlorinated to remove tramp impurities. The peak temperature of this process did not exceed 1400degreesC. Chemical analysis results showed the level of impurities removed. High-temperature mass spectrometry results as a function of increased temperature showed how the volatilization behavior of zircon changed after carbochlorination. High-temperature (1400degreesC) modulus of rupture tests were performed, and no degradation in average strength to failure was observed. Little or no change in bulk density, porosity, or zircon microstructure was observed. Carbochlorinated zircon refractories were used to build production-sized glassmaking furnaces for manufacturing high-optical-quality glass.