﻿Vol. 66.~] ON THE GEOLOGY OF NYASALAND. 197 



off into the other, and few veins or reefs of quartz are to be found 

 entirely free from felspar. Tourmaline is widely distributed in 

 these veins, especially in the more typical pegmatites. As a rule, 

 the tourmaline occurs in large well-formed crystals, but the streaked 

 and banded tourmaline-quartz veins of the plateau-region behind 

 Neno approach more closely to schorl-rock. The frequent occur- 

 rence of felspar, and more rarely tourmaline, in the quartz-veins of 

 Nyasaland, lends colour to the belief that they represent the 

 mother-liquor of an igneous magma rather than the products of 

 lateral secretion. 



Very rarely has any connexion been observed between the 

 distribution of the quartz and pegmatite-veins and that of the 

 plutonic masses. Near Dowa, in Central Angonaland, however, 

 typical pegmatite-veins and dykes are very abundant, and increase 

 in number and width when traced towards the large mass of coarse- 

 grained granite already mentioned. The thicker bands of pegmatite 

 not infrequently show graphic intergrowths between the quartz 

 and the felspar. The quartz varies in colour from grey to mauve, 

 and even black. These graphic pegmatites have, therefore, a very 

 distinctive appearance. 



(b) The Sedimentary Groups. 



The following divisions have been recognized among the later 

 sedimentary rocks of Nyasaland : — 



3. Kecent deposits. 

 2. The Karroo Series. 

 1. The Mafingi Series. 



(1) The Mafingi Series. — The rocks of the Mafingi Series 

 form an isolated group of mountains in the north-western corner 

 of Nyasaland, and cross the border into North-Eastern Rhodesia. 

 The Mafingi Mountains range for about 18 miles in a north-and- 

 south direction, and rise to over 7000 feet above sea-level, or 

 nearly 3000 feet above the surrounding plateaux. This mountain- 

 group consists of steep, bare, scarp-like ridges separated by deep 

 and narrow V-shaped valleys, a type of scenery not to be found 

 elsewhere in the country. High mountains of gneiss lie along the 

 eastern edge of the wide Mbalise Valley, and afford with their 

 softer outlines a striking contrast to the rugged quartzite-ranges of 

 the Mafingi just across the valley. 



The Mafingi Series consists of a great thickness of whitish 

 quartzites with phyllitic bands, schistose flags, felspathic sandstones, 

 and grits. According to a traverse made in an east-south-easterly 

 direction, from the upper waters of the Luangwa in North-Eastern 

 Rhodesia to Kayalise village on the Mbalise River, it appears that 

 the series may be roughly divided into the following groups, in 

 descending order : — 



