3.1 The zircon content and bulk density of a zirconia-silica refractory material have important influences on chemical resistance and its satisfactory use in refractory applications. This classification is considered useful for purchase specifications and quality control.

1.1 This classification covers fired refractory brick and shapes consisting predominantly of zircon (ZrO₂·SiO ₂) and containing, by chemical analysis, not less than 60 % zirconium oxide (ZrO₂) and not less than 30 % silica (SiO ₂).

1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.