a. A clay consisting of a mixture of bauxitic minerals, such as gibbsite
and diaspore, with clay minerals, the former constituting not over 50% of
the total. The opposite of this would be an argillaceous bauxite.
ACSB, 1 b. A natural mixture of bauxite and clay, containing not less than 47% nor
more than 65% alumina on a calcined basis. Harbison-Walker
Dictionary of Mining, Mineral, and Related Terms