gneiss
/ˈnaɪs/ noun
Forms gneisses
- noun (geology) A common and widely-distributed metamorphic rock having bands or veins, but not schistose.
Etymology
From German Gneis, from Middle High German gneist (“spark”), from Old High German gneisto (“spark”). More at gnast.
Webster’s 1913
- noun A crystalline rock, consisting, like granite, of quartz, feldspar, and mica, but having these materials, especially the mica, arranged in planes, so that it breaks rather easily into coarse slabs or flags. Hornblende sometimes takes the place of the mica, and it is then called hornblendic or syenitic gneiss. Similar varieties of related rocks are also called gneiss.
Etymology [G.]
Sources: Wiktionary · Webster’s 1913 — from the Wiktionary entry “gneiss”, CC BY-SA 4.0. Details