154 THE REGION OF THE BARUjfe 



to which so many thousands of square miles of the 

 Angoni country belong. It is one of course which 

 has been but little explored, either from the pro- 

 spector's or any other point of view. The most 

 prominent feature consists of constantly occurring 

 masses of granite rocks traversed by quartz reefs. 

 These appear not only in the form of isolated 

 mountainous masses, but crop out of the soil like a 

 bare stone floor for areas many acres in extent. 

 Then again, surrounding the mountain bases, are 

 strewn rounded boulders from two or three to 

 many thousands of tons in weight. In some of 

 these felspar occurs porphyritically, exhibiting a 

 singular system of curious veins probably caused, as 

 it has been suggested to me, by the conditions in 

 which they were originally cooled. The varieties 

 of granite most commonly met with contain clear 

 grains of quartz without cleavage, also orthoclase 

 and brown and black mica. Aplite shows itself in 

 the form of small veins, and appears to consist of 

 orthoclase and quartz without additional accessory 

 minerals. The colour is of a dull yellow, the veins 

 coarse-grained, compact, and much stained, perhaps 

 by solutions of iron. Tourmaline granite is 

 extremely common, as is shorl rock, whilst, in some 

 of the stony masses which I examined, magnetite 

 occurs with small visible garnets, as also large 

 masses of what has been described to me as 

 pegmatite. Here, however, the quartz particles 

 are embedded in the darker felspar and betray 

 considerable cleavages. In some of the outcrop 

 surrounding Ngaru, hornblende is met with, whilst 

 some of the porphyrites are probably not dissimilar 



