R. R. Walls — TJie Geology of Portuguese Nyasaland. 205 



The material, strange to say, is never found of a slaty structure, 

 although occurring in highly foliated rock. These black bands 

 in the gneiss were often found in the neighbourhood of graphite 

 schist, and suggested some connexion in origin which could not 

 now be recognized in the metamorphic state. 



Bitumen and coal are occasionally found in the valleys of the 

 Eovnma and Lujenda, and were first commented on by Livingstone. 

 Both are of a very shaly nature, and the carbon percentage is small. 

 The discovery, however, gave rise to fantastic tales of rich coal- 

 fields, and several expeditions were sent oat at various times to 

 search for coalfields, with no success whatever. The most important 

 expedition was Thomson's in 1881, when he went out to investigate 

 for the Sultan of Zanzibar, who then exercised jurisdiction over 

 this area. The most noted outcrop of this so-called coal is at Itule, 

 on the Lujenda River, but only a few seams of a few inches thickness 

 are known altogether. Owing to the folding the beds are lenticular 

 and not extensive and therefore of no commercial importance. 

 Their occiirrence, however, is interestuig from the geological point 

 of view, and may ijidicate that the rocks in that neighbourhood are 

 of true Carboniferous age. Thomson assumed that these rocks were 

 of Carboniferous age, and let down into the gneisses by trough 

 faidting, but he made no attempt to map the foliation of the rocks 

 carefully in the districts over which he travelled. It is worthy of 

 note that these carbonaceous bands occur themselves in highly 

 metamorphic rock, and seem to have themselves suffered in the 

 metamorphism, e.g. the transformation of coal into bitumen. The' 

 thin black bands of anthracite-looking material in the gneisses were 

 also noted by Thomson. In the present state of our knowledge it 

 would not be wise to correlate the thin black bands in the gneisses 

 throughout the country generally with the one or two seams of shaly 

 coal or bitumen found at Itule on the Lujenda. 



The valley of the Lurio in the extreme south of Portuguese 

 Nyasaland is remarkable as being made up of banded quartzites, 

 with little or no gneiss and inconspicuous mica. These quartzites 

 are particularly hard and strongly marked off in colours of black, 

 red, yellow, white, brown, purple, etc. In fact, they should be 

 more properly termed banded jaspers. For 150 miles up the 

 river, and possibly much more, these quartzites all dip to the 

 north, generally at angles of about 50 degrees. The Lurio valley 

 is many miles wide, and it. is practically all composed of quartzites ; 

 yet the exact width of these quartzites is difficult to determine as 

 they seem to grade into the gneisses in some places. More often, 

 however, intrusive granite is found along what appears to be the 

 line of junction. Across the valley in the territory of Mozambique 

 in the south the gneisses could be seen again as huge corrugated 

 moimtains along the sky-line. Very occasionally the quartzites 

 show sedimentary origin and beds of rounded flints appear. These 

 are not common however. The quartzites of the Lurio have many 



