The tertiary reaction is the higher aluminum fluoride complexes continue to react with clay, producing the lower aluminum fluoride complexes and silica gel.

Natural Resources: natural gas, crude oil, silica, limestone, clay, chalk, gypsum, iron, salt, lead, tin.

A comparative test of standard clay bricks, high alumina bricks, silica bricks and periclase bricks which were used as checkers in upper parts of regenerators has been conducted.