gneiss
Concise Oxford English Dictionary © 2008 Oxford University Press:
gneiss /nʌɪs/
▶noun a typically coarse-grained metamorphic rock with a banded or foliated structure.
– derivatives
gneissic adjective,
gneissose adjective.
gneissic adjective,
gneissose adjective.
– origin C18: from Ger., from Old High Ger. gneisto ‘spark’ (because of the rock's sheen).
'gneiss' also found in these Oxford entries:

