augengneiss

plural augengneisses

1. countableuncountableA type of metamorphic rock characterized by large, lenticular mineral grains or crystal aggregates (usually feldspar or quartz grains that have been deformed during metamorphism), resembling eyes, embedded within a finer-grained matrix.

   Rocks of this migmatitic formation, having a smaller quantity of neosome, are augengneisses.

   1964, Bruno Zanettin, Geology and Pertrology of Haramosh-mango Gusor Area (Italian Expeditions to the Karakorum (K²) and Hindu Kush SCIENTIFIC REPORTS; III - Geology - Petrology), volume I, Brill Archive, page 8

   2 more examples

   The term ‘Augengneiss’ has a definite use in German petrography, and is properly used to denote those gneisses "in which single large felspar-masses (orthoclase), in form ranging from the blunt lenticular to the approximately spherical, occur, segregated from the matrix of the rock which possesses a schistose (schieferig) or coarse grained (flaserig) structure, and around which the mica-laminæ adhere."

   1889, A. IRVING, CHEMICAL AND PHYSICAL STUDIES int the METAMORPHISM of ROCKS based on A THESIS (WITH APPENDICES) WRITTEN FOR THE DOCTORATE IN SCIENCE IN THE UNIVERSITY OF LONDON., page 67

   In the Canigou Massif the group’s metasediments together with the gneisses and the augengneisses were folded into a gigantic flat-lying isoclinal fold.

   2023 September 16, Wikipedia contributors, “Canaveilles Group”, in English Wikipedia, Wikimedia Foundation