‖ augen
(ˈaʊgən)
[pl. of G. auge eye n.1]
Applied to a variety of gneissic rock containing eye-shaped masses of feldspar or quartz; porphyritic gneiss; esp. augen-gneiss.
| 1885 A. Geikie Text-bk. Geol. (ed. 2) vii. 132 Porphyritic gneiss or Augengneiss, in which large eye-like kernels of orthoclase are dispersed. 1910 Encycl. Brit. XII. 149/2 When large felspars, of rounded or elliptical form, are visible in the gneiss, it is said to have augen structure. Ibid. 352/2 The larger crystals are converted into lenticular or elliptical ‘augen’. 1925 N. E. Odell in E. F. Norton Fight for Everest, 1924 iii. iii. 297 It would certainly appear that the augen variety [of gneisses] were the younger and intrusive facies. 1940 C. M. Rice Dict. Geol. Terms 27/2 Augengneiss, a general term for gneissose rocks,..containing ‘eyes’, i.e., phacoidal or lenticular crystals, or aggregates, which simulate the porphyritic crystals of igneous rocks. |