Granite-Gneiss | Article about Granite-Gneiss by The Free ...
Granite-Gneiss. a holocrystalline shale rock consisting, like granite, of quartz, potash feldspar, acid plagioclase, and mica (predominantly biotite). A majority of researchers believe granite-gneisses to be granites that have crystallized deep in the earth's crust either during the cooling of the magmatic melt under directed pressure or ...