LTDENBUEG AXD DE KAAP, TRANSVAAL, SOUTH APRICA. 



583 



The gold lodes consist of main qnartz-reefs and transverse leaders ; 

 "These leaders are thin (a few inches onlj- in thickness), and 

 consist partly of white quartz, partly of oxide of iron and man- 

 ganese. Two of them sometimes merge into one, and occasionally 

 two or more unite to form a main lode close to or in contact with 

 the dyke. Almost without exception the gold-mines of this district 

 are in such leaders in proximity to diorite dykes." An average 

 yield of 4 oz. of gold to 2000 lb. of quartz was the estimated 

 result of several examinations. 



Several main and branch dykes of diorite are traceable for long 

 distances, and in some instances are well exposed in the open mines. 

 In two cases the shales are sharply tilted by the dykes on the west 



w. 



Fig. 3. — Section of Diorite Dyhe, Lishon-Berlyn. 



E. 



a. Tilted shale. 



b. Dyke. 



side, and in one on the east they are slightly contorted on the other 

 side. In the section the weathering leaves hard kernels of blue 

 diorite with concentric rings, semidecomposed, shading off into the 

 soft brown mass, which otherwise resembles an alluvial loam., 



v. A few miles S.W. of Waterfall are the farms about " Pilgrim's 

 Rest," belonging to the Transvaal Gold-Land-and-Exploration 

 Company. The rocks here are higher in the series and are more 

 siliceous in character, the lower main mass of chalcedolites being 

 in considerable force. Their chief outcrop, however, is along 

 the west side of the Blyde Eiver. Here, also, are many diorite 

 dykes, one of which, a small branch dj'ke in Pilgrim's-Eest Creek, 

 has tilted the adjacent beds inversely to the usual position. 

 "With the exception of the rich alluvial deposits in the creek, the 

 ground chiefly worked here for gold has been the " rotten-reef," 

 similar to those previously described. The chief of these are at 

 Erown's Hill and Ophir Hill ; but I have no data upon which to 

 base an opinion as to their value, which is regarded as high. 



Crossing the Blyde and mounting the steep escarpment to the 

 west, we find shales cropping out from top to bottom, with the ex- 

 ception of the upper of the two main series of chalcedolites inter- 

 vening part way up the hill. The shales have generally a small 

 westerly dip, but are locally thrown to high angles and into various 

 positions by plutonic dykes. The chalcedolites are much decom- 

 posed, and a bed of quartz, at least one foot in thickness, is seen 

 amongst them. On the summit of the hill is a series of crystalline 

 sandstones. 



