a. [f. prec. + -IC: cf. F. trachytique.] Consisting, or of the nature, of trachyte; containing, or abounding in, trachyte.
1827. Edin. Rev., XLV. 320. Those hills consist of a trachytic formation.
1830. Lyell, Princ. Geol., I. 396. Where it [felspar] is in great excess lavas are called trachytic; where augite (or pyroxene) predominates, they are called basaltic.
1833–4. J. Phillips, in Encycl. Metrop. (1845), VI. 767/1. Trachytic porphyry … occurs on the Western shore of the Island of Arran.
1869. Phillips, Vesuv., viii. 211. Slopes of crumbling tufaceous, pumiceous and trachytic rocks.
