Waring: Geology of Northeastern Brazil. 187 



common, but black tourmaline seems to be more In evidence in them. 

 Knolls of granite or coarsely banded gneiss rise above the mean level. 

 Westward from Soledade the strike of the gneiss swings slightly to 

 nearly west, with steep south dip. Thirty kilometers from Soledade a 

 small granite range trends N. 70° W., magnetic, or nearly west, true. 

 West of this range some variation in the strike was observed, from 

 about N. 60° W. to due west. Occasional pegmatite dikes seem to 

 have the same strike as the gneiss. Schist, or perhaps finely laminated 

 phases of the gneiss, also exhibit the same uniform strike, with steep 

 south dip. Ten or 12 kilometers northeast of Batalhao thinly-foliated 

 mica-schist, much disintegrated, produces an uneven topography. 

 Seven or eight kilometers east of Batalhao a dark mica-schist, striking 

 N. 60° W., and dipping steeply southward, forms prominent though 

 small ledges, distributed over the surface so as to resemble grave- 

 stones. Toward Batalhao the material becomes coarser in texture, 

 and near this town the principal rock is a porphyritic feldspar gneiss. 

 At several places in the river near this place, ledges striking west 

 extend nearly across the channel. The slopes on each side of the 

 stream expose material of a more granitic texture. Northward a 

 gently rolling plain of coarse-grained gneiss exhibits strikes of N. 70° 

 W., to S. 70° W., with the usual steep south dip. A small stream fif- 

 teen kilometers from Batalhao has cut a deep valley in the mica-schist, 

 which had been crossed by me farther to the east. More resistant 

 gneiss is thence exposed at intervals to Viragao. The road then 

 crosses a small range of light-colored micaceous quartz-schist, which 

 in places crumbles to sand and resembles a sandstone. Two kilometers 

 east of the road a white ledge, seemingly of quartzite, dips northward 

 at an angle of thirty degrees. In the lowland along the north base 

 of the range dark-green gneiss strikes southwest, with steep south- 

 east dip. Dark mica-schist, thinly foliated and carrying much quartz, 

 is exposed in a low divide three kilometers southwest of Periquitos. 

 Along the course of a small stream north of this place white quartzite 

 seems to lie nearly horizontally over dark gneiss, which contains a 

 green mineral, probably chlorite, and brown garnets up to three or four 

 millimeters in diameter. Four kilometers north of Periquitos a small 

 spring issues from beneath a prominent quartzite ledge, which strikes 

 S. 25° W., with dip of thirty-five degrees westward. In the vicinity 

 both quartzite and pegmatite form ledges in the gneiss area, as shown 

 on Plate VI, fig. i, which also shows what seems to be a quartzite- 



