-smectite-

n. [ G. smectit, fr. Gr. &unr_;&unr_;&unr_;&unr_;&unr_; a kind of fuller's earth, fr. &unr_;&unr_;&unr_;&unr_;&unr_; to wipe off. ] (Min.) A hydrous silicate of alumina, of a greenish color, which, in certain states of humidity, appears transparent and almost gelatinous. [ 1913 Webster ]