Gneiss. A metamorphic foliated rock formed from sedimentary (paragneiss) or magmatic (orthogneiss) rock at considerable depths in the earth's crust under high temperatures and pressure. Containing quartz, feldspar, and mica, along with granite it is a basic rock of the Ukrainian Crystalline Shield. It is found also in the Maramureş-Bukovynian Upland. Gneiss is used mostly as aggregate, paving stone, and facing material.