GEOLOGY AXD MINERALOGY OF NATAL. 125 



are generally to be seen as dyke-like masses intruding the ancient 

 rocks. More often than not they cut the schistose rocks at almost 

 right angles to the ])lanes of foliation. They also appear to have 

 filled in fissures and rents in the schists in an irregular manner. 

 The}' vary in thickness from a few inches to a few feet, and consist 

 essentially of an admixture of felspar and quartz, the felspar nearly 

 always being orthoclase. It is often in a good state of preservation. 

 A glance at its cleavage planes often reveals the fact of decomj^osition 

 having commenced. Garnets and mica are also to be found at 

 times in tliese pegmatites. 



At the line of contact of these veins and within a short distance on 

 either side the regularity and definition of the joint planes in the 

 adjoining rocks are most marked. They often appear to have been 

 formed in a joint plane. Those that appear to belong to the earlier 

 period have undoubtedly shared the fate of the other ancient rocks 

 in the metamorphic disturbances. They also aj^pear to consist and 

 have consisted of an admixture of felspar, quartz, with occasional 

 garnets and a little mica. I say "have consisted" in order the better 

 to explain their connection with a system of quartz veins or leaders 

 found traversing the Swazieland schists. These leaders, if thus I 

 may call them, have a general line of strike across the country' of 

 N.E. by S.\\\ They vary in size and thickness from a mere paper- 

 like tissue to several feet. They also apj^ear to be confined to- 

 certain definite belts in these schistose rocks. I have noticed what 

 appears to be two different belts at least — a lower and a higher one.. 

 The difference is one merely of separation I think and not of age- 

 Within each belt these quartz leaders seem to vary in number. 

 They seem to traverse the gneiss and schist in a direction parallel 

 to and along the line of foliation, and are continually narrowing in 

 and widening out throughout their course. They are often lenticular. 

 They also agree with the other rocks in variability and angle of dip. 

 The dip varies from J5 to 84" in a south-easterly, southerly, or 

 south-westerly direction. Their outcrop traverses the sides and 

 summits of the hills in a most sinuous manner. Where they are 

 found cropping out on the summits or edges of hills or ridges, their 

 breadth appears to attain the maximum of thickness. They are at 

 times found enclosing pieces of schist between them. -J 



At the junction of some of these leaders with the adjoining 

 schists and gneiss no distinction can be drawn lietween them and 

 the quartz elements in the other rocks. Both are clear and glassy. 

 Where, however, they have suffered greatest from metamorphism 

 the quartz is more often of a reddish tinge, and their line of contact 

 is readily distinguishable. Besides, their lenticles are crushed and 

 cracked in various directions and the schists show much sericite 

 near the line of contact. There is usually a film of iron oxide 

 between the schists and the lenticle of quartz. Furthermore, iron 

 oxide and other stainings are apparent in their cracks. 



The same kind of felspar which is so frequently found in the 

 earlier pegmatites is also to be found in these ' ' leaders ' ' along their 

 entire length at different parts : it is often most sparingly dis- 

 tributed. One may follow along a leader for 100 feet and more 

 and not see a trace of felspar, but within the next few feet of its 



