argilliteMin.|ˈɑːdʒɪlaɪt| [f. as prec. + -ite.] Argillaceous schist, clay slate. argiˈllitica., of or containing argillite. Craig, 1847. 1795Mills in Phil.Trans. LXXXVI. 39 Bare rocks..a variety of argillite.1850Dana Geol. xiii. 564 The rock somewhat resembles an argillite.