part 1] AND ASSOCIATED EOCKS OF MOZAMBIQUE. 41 



fragments of the older biotite-gneiss. In the Nrassi Basin itself, 

 there are many coarse pegmatites, some of which are rich in 

 tourmaline. Of still later age are a few north-and-south pyro- 

 xenite dykes, which (like the crystalline limestones) are exposed 

 in a gully east of Ericola. 



(e) Fort Chinga District. 



Passing now to the plateau south-east of the Chika range, we 

 find (along the disused Portuguese road that runs from Chinga 

 towards the isolated peak of Mushima) bands of garnetiferous 

 gneiss among the normal biotite-gneisses. The gneisses here 

 are thickly threaded with grey granulitic pegmatite, and intruded 

 into locally by extremely coarse pegmatite-dykes, in some of which 

 individual crystals of red felspar occupy the whole width of the 

 dyke and extend for several feet. Some of these pegmatites carry 

 tourmaline, and near the surface yellow-green crystals of autunite 

 .are occasionally present. 



(/) West of Ribawe. 



I am indebted to Mr. D. A. Wray for permission to use a series 

 of notes on the rocks encountered by him during his journeys from 

 "the Memba Minerals base-camp at Sawa to the Ina'go and Xamuli 

 Mountains in the west, and to the Luli Valley and Mluli Moun- 

 tains in the north-west. In the district north of the Norray 

 Peaks, the biotite-gneisses are accompanied by bands of horn- 

 blende-gneiss, garnet-gneiss, eclogite, and garnet-pyroxene-scapolite 

 rocks, the whole series dipping at a high angle towards the north- 

 west and striking uniformly along a north-east and south-west 

 direction. In the same line of strike, 40 miles away to the south- 

 west, garnet- and hornblende-gneisses again appear, exposed in the 

 Mrayho Hills. The complex north of the Nbrray Peaks is riddled 

 as usual with grey granulitic pegmatites, and has been penetrated 

 at a later date by coarse tourmaline-bearing pegmatite. Farther 

 north, in the valley of the Namikati River (draining the south- 

 eastern slopes of the Mluli peaks), there are also composite 

 garnetiferous and hornblende-gneisses in which large crystals of 

 tourmaline and magnetite occur. 



The Mrupi peaks are made up almost entirely of coarsely-banded 

 hornblende-gneiss, remarkable in the fact that the dip of the 

 banding is almost vertical, while the surrounding biotite-gneisses — 

 generally fine-grained — have a nearly horizontal foliation, a feature 

 that characterizes them all along the Luli Valle}" as far west as the 

 Falls near Vattiva, where the gneisses are highly contorted and 

 again very coarse in structure. 



The huge peaks of the Inago Mountains consist of a grey biotite- 

 granite showing fluxion -structure, which passes peripherally into 

 gneiss containing a much higher percentage of biotite. The 

 hamuli Peaks, though seen only from a distance, appear to 



