'80 DR. A. HOLMES ON THE PRE-CAMBRIAX [vol. lxxiv, 



ilmenite is present in many of the pegmatites, and similar rocks 

 occur in the north-eastern part of Mozambique around Niveta. 



On the banks of the Nrassi River, due east of Ericola, 

 Mr. Way land found a felspathic pegmatite veined with pyrite and 

 capped with bauxite. Pyrite and other sulphide minerals were 

 also found by Mr. E. W. E. Barton, the leader of the Memba 

 Minerals Expedition, in coarse pegmatite-dykes occurring near 

 Nakota in the south of the territory. 



Many of the pegmatites carry big crystals of black tourmaline, 

 and in the coastal districts, tourmalinized rocks are especially 

 abundant. Around Memba many of the pegmatites are rich in 

 -tourmaline and muscovite, and locally the rocks are made up 

 :almost entirely of these minerals. Others approach tourmaline- 

 granite in their texture, while the Post Office at Memba is huilt on 

 .an outcrop of a typical schorl-rock. Near Ibrahimo, quartz-mica- 

 granulite carries small crystals of tourmaline that have probably 

 been introduced from tourmaline-bearing pegmatites which cut the 

 older rocks. Black tourmaline also occurs in many of the peg- 

 matites of the Nrassi, Bibawe, Fort Chinga, and Noway districts. 

 Near Fort Ligonia, on the Zambesi side of the river, fragments of 

 :red and pink tourmaline associated with lepidolite were found 

 in the debris overlying the muscovite- granites, but the parent rock 

 was not seen. 



(4) Quartz- Veins. 



Veins of quartz varying from a few inches to man} r feet in 

 thickness are widely distributed in the territory ; but, apart from 

 pyrite and accompanying rusty staining, they were, with one excep- 

 tion, free from mineralization. The exception refers to the quartz- 

 veins of Niveta, in the north-east of Mozambique, which have been 

 reported to carry considerahle quantities of massive galena. These 

 veins are directly connected with red felspathic pegmatites. A 

 similar relationship was found on the north-western side of Mhala, 

 Nakavala, where a quartz-vein 12 inches thick, was traced towards 

 the hill, and found to become increasingly felspathic. 



VIII. The Pyroxenite- and Picrite-Dykes. 



(1) Pyroxenites. 



In the Nrassi Basin (PL XI) occur a number of dykes of pyro- 

 xenite that follow a nearly north -and- south direction. In a gully 

 draining into the Nrassi from the slopes of Ericola, and about half 

 ;a mile from the hase of the hill, two of these dykes (J¥os. 33 Sf 34) 

 •can be seen cutting through the youngest pegmatites ; and con- 

 sequently they are demonstrably the youngest intrusions of the 

 district. The dykes are generally 2 or 3 feet wide. They appear to 



