Rift valley, overlying a formation of granite, gneiss and quartz.
The rocks of its lower half are mainly granite and gneiss; its upper half is composed of porphyritic greenstone, and a variety of minerals occur.
The Cordillera, which bounds them on the west, is formed of folded beds, while the Sierras which rise in their midst, consist mainly of gneiss, granite and schist.
The most valuable immediate product of the state's mines and quarries for nearly every year from 1890 to 1908 was building stones of granite and gneiss, which are found in all parts of the state west of the " Fall Line "; the best grades of granite are quarried chiefly in Gaston, Iredell, Rowan, Surry and Wilkes counties.
In Unst the high ground on the west coast consists of gneiss, which is followed eastward by schists of various kinds, then by a belt of serpentine, 2 m.