ilesiteMin.|ˈaɪlzaɪt| [Named, 1881, after M. W. Iles, who described it.] Hydrous sulphate of manganese, zinc, and iron, resulting from the decomposition of pyrite and sphalerite. 1881Amer.Jrnl.Sc.Ser. iii. XXII. 490 Ilesite, a white friable mineral with a bitter, astringent taste.