a. [f. Gr. ἄπυρ-ος without fire, unsmelted (f. ἀ priv. + πυρ- fire) + -OUS. Cf. Fr. apyre.] Not altered by exposure to fire.
1782. Wedgwood, in Phil. Trans., LXXII. 309. A clay sufficiently apyrous or unvitrescible.
1802. Bournon, ibid., XCII. 323. Haüy … gives it the name of apyrous felspar.
