436 Major G. W. Williams — 



exposed in large, slightly convex bosses. In the bed of the Sabon- 

 Garri River is an exposure of a coarse-textured granulitized microcline 

 granite of highly acid characteristics (103), and immediately north 

 is a small well-weathered exposure of highly foliated muscovite 

 granite. The village of Sabon-Garri lies at the foot of three domes 

 of granite (105). 



From the village to Duchin Chanya Cherigi (lit. the hill that resembles 

 a pigeon's breast — another example of apt nomenclature), the track 

 runs in a general northerly direction, passing between numerous 

 ridges and domes of Sabon-Garri granite. Aplitic intrusions are not 

 uncommon. Approaching Chanya Cherigi foliation increases and in 

 many places the granites are strongly gneissose (106). 



The dark mass of Chanya Cherigi, 3,369 feet, which rises 1,000 feet 

 above the plain level, forms a conspicuous landmark. This hill is 

 the highest of a series of granite hills, oval in ground plan, the longer 

 axis running due north and south. The granites in the neighbour- 

 hood show marked effects of dynamo-metamorphism. The general 

 foliation is north and south, and the main crush zone, which extends 

 through Gora Hill and Chanya Cherigi, is well mineralized. A well- 

 defined lode forms the crest of these two hills, and is traceable for 

 some 2 J to 3 miles south and north. Tin and wolfram occur in 

 narrow, parallel, quartz-filled veins. The country rock is an 

 altered granite containing topaz. (C.C. 4-7.) Numerous lenticular 

 masses of aplite occur in the immediate Jieighbourhood. (C.C. 2 -3.) 



Many exceedingly rich " floaters " of tin ore (some assaying up to 

 50 per cent, SnOg) occur on the slopes of the hills and in the valley 

 below. Some of these "floaters" are exactly similar in appearance 

 to the rich ore from the " Bushveld " tin mines (South Africa). In 

 places the granite on the slopes of the valleys tends to weather into 

 flat sheets, but the usual weathering is into rough blocks ; many of 

 the isolated boulders display a tendency to " mushroom " shape, 

 due to the erosion by blown sand. 



In the vicinity of Yarde Gongome, the main camp of the Yarde 

 Kerri mines, the prevailing rocks are gneisses, and these extend 

 northwards to Burra, at the western end of the Ningi Hills. North- 

 east and east from Yarde Gongome the Sabon-Garri granites come 

 in, and form a group of characteristic domes in the neighbourhood 

 of Minna camp and near to Dogon Daji on the Minna stream. 



The boundary between the Sabon-Garri granites and the gneisses 

 is ill-defined. Contact metamorphism is entirely lacking, and 

 masses of gneiss are frequently included in the granites. In the 

 neighbourhood of Keffi Filani veins of pegmatite cross and recross 

 the boundary, and the whole contact is foliated in a general equatorial 

 direction. This foliation, which afiects both granites and gneisses, 

 was probably induced by the intrusion of the Ningi granites, the 

 longer axis of which runs due east and west. 



The dominant foliation in the country between Chow and Chanya 

 Cherigi is distinctly meridional. Between Dogon Daji and KeflB. 



