Augengneiss
noun ·Rare ·Advanced level
Definitions
- 1 A type of metamorphic rock characterized by large, lenticular mineral grains or crystal aggregates that resemble "eyes" (called augen in German) embedded within a finer-grained matrix. These "eyes" are usually feldspar or quartz grains that have been deformed during metamorphism.
"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.""
Example
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.""
Etymology
From German Augen + gneiss
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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.