gneiss, a dense, tough, coarse-grained rock (pronounced ‘nice’) in which distinct bands have developed, distinguishing it from other metamorphic rocks. These irregular bands, typically of paler feldspar and quartz alternating with darker biotite or amphibole, range in thickness over a few millimetres to centimetres with an irregularity that distinguishes the appearance of gneiss from the layers seen in some sedimentary rocks (see geology). It is resistant to weathering and usually yields thin, rather acid soils but it is surpringly common in vineyards, for example, in austria’s Kamptal and Wachau regions, in muscadet, roussillon, and côte Rôtie in France, in parts of the US state of virginia, and in canada’s Okanagan Valley.
