nise, a rock, composed of quartz, feldspar and mica, arranged in layers. The layers, whether straight or curved, are frequently thick, but often they vary considerably in the same specimen. Gneiss passes on one side into granite, from which it differs in its foliated structure, and on the other into mica slate. It is rich in metallic ores, such as gold, silver, cobalt, antimony, copper and iron, but it contains no fossil remains. Porphyritic gneiss presents large, distinct crystals of feldspar, which traverse several of the foliated layers. Gneiss often contains hornblende, in place of mica, and then receives the name of syenitic gneiss. The only difference between this rock and granite consists in the structure, the materials of granite being crystallized promiscuously, those of gneiss being separated in layers. It is the principal rock of very extensive districts; it predominates in Norway and through all the north of Europe. It abounds in the Southern Alps and the Pyrenees and forms the loftiest chains of the Andes of Quito. In the United States, gneiss is a common rock, especially in New England and the eastern and southern parts of New York. See GRANITE; MICA.