They carry brittle crystals of black tourmaline, garnet, and muscovite mica. East of Ballena the rock becomes coarser and somewhat gneissose, with an abundance of mica. There are no bedding planes, simply a parallelism of constituents. This schistose structure has a northwest direction. The gneiss changes to mica schist on the grade above Santa Ysabel. The schist alternates with occasional strata of quartzite; strike north 25° west. The quartzite is a white, fine, granular variety, containing a little mica. Coarse gneiss outcrops again farther up the grade; at the top it becomes finer, carrying some hornblende, and alternating with strata of fine mica schist; dip northeast. The gneiss often becomes granitoid. The lamination has no constant direction, and resembles a flowage structure. This granitoid gneiss extends to within a mile of Julian, when there is quite a sharp transition to a gneissoid mica schist. That gives place to a fine schist, and a quarter of a mile west of Julian to a pearly hydro-mica schist. The schists strike north 20° to 30° west, dip 70° northeast. At Julian the rock is a dark, thin-bedded mica schist, usually termed a slate. There are also dark felsitic rocks and some gneisses. The belt of dark slaty mica schists is about half a mile wide. Toward the Balkan Mountain the rocks become more gneissoid. This mountain seems to be formed wholly of gneiss and mica schist. In some places the rock is nearly massive, and contains a large amount of quartz. The rocks forming the mountains near the road from San Felipe to Vallecito are nearly all gneissoid. The real desert begins on leaving San Felipe Valley. The road extends southeast for 5 miles and then turns southwest, descending a narrow, rocky gorge to the head of Vallecito Creek. Near where the road turns to the southwest, the gneisses are cut by innumerable dikes of coarse granitic composition. Many of these run parallel, cutting across the strike of the gneisses, and give the appearance of a bedded formation. In the cañon, before reaching Vallecito Creek, mica schist appears. It is bent and twisted into every conceivable direction, and varies exceedingly in structure and composition in the course of a few feet. The dip is northeast, and often at a small angle. The granite dikes often carry garnets, being quite similar to those between Julian and Banner. They were probably intruded after the eruption of the granite, and the related metamorphism. At Mason’s granite and gneiss both appear as intrusives in the schists, and are themselves cut by coarse dikes similar to those described. Between this point and Banner, in a direct line, gneiss is the prevailing rock. The high mountain east of Banner is more granitoid.