ˈnīs noun
( -es )
Etymology: German gneis, probably alteration of Middle High German gneiste, ganeiste spark, from Old High German gneisto; akin to Old English gnāst spark, Old Norse gneisti
: a laminated or foliated metamorphic rock corresponding in composition to granite or some other feldspathic plutonic rock and often named for a conspicuous mineral constituent
biotite gneiss
hornblendic gneiss
or for the plutonic or sedimentary rock of origin
syenitic gneiss
conglomerate gneiss
— see orthogneiss , paragneiss
• gneiss·ic -sik adjective
• gneiss·ose -ˌsōs adjective