132 GEOLO(;V (JF THE NEIGHBOUR HdOD OF STKLLKX i!( )S( II . 



appearance from that of Table Motintain. Black micaceous 

 patches, representing altered slate inclusions, are fairly numer- 

 ous, and little pockets of black tourmaline are also found. Veins 

 of pegmatite and aplite are common, and some of these run out 

 some little distance into the slate. I have already described the 

 veins and inclusions of this granite mass* and need not refer 

 to them further. 



The Malmesbury rocks, hardened and altered by contact t(^ 

 chiastolite-hornfels. are exposed only a short distance up-stream 

 from the bridge, so at this point the granite margin can be fixed 

 with precision. From here the boundary runs in a north- 

 westerly direction towards Bottelary Hill, but it cannot be placer! 

 accurately on account of the thick overburden. Papegaaisberg 

 itself, save only the south-west side, and the whole ridge right 

 north to Koelenhof, consist entirely of Alalmesbury rocks, show- 

 ing evidence of contact alteration. South of Papegaaisberg the 

 contact disappears under the alluvium for half-a-mile, after which 

 the granite reappears in a long, low ridge to the west of the 

 Somerset Road. The granite in this ridge is of very variable 

 texture, and in part of rather fine grain, which suggests the 

 close proximitv of the contact surface. Malmesbury rocks are 

 not exposed here, however, nor are they to be seen luuil one 

 climbs up intt) some of the kloofs which descend from Stellen- 

 bosch Mountain. In these kloofs and on the lower slopes of the 

 mountain one gets occasional evidence of the continuation of a 

 belt of Malmesbury rocks along the west side of the mountain 

 as far as the Blaauwklip Stream ; beyond this, right into the 

 Hoek of Helderberg, only granite is exposed. The line of junc- 

 tion can therefore be laid down pretty accurately, although it is 

 not actually visible at any point. 



This eastern margin of the granite oitght to possess an 

 especial interest, since the western margin is highly mineralized 

 at Kuil's River, and yields tinstone, wolfram and arsenopyrite. 

 The abundance of tourmaline veinules in the granite about Bos- 

 man's Crossing and at Vlottenberg show that there has been 

 active mineralization on the east side as well as the west. Some 

 veins of arsenical pyrites (according to an analysis by Dr. van 

 der Riet, the actual species is lollingite) occur in the ^iranite on 

 the farm Bonte River, at Helderberg, and molybdenite has also 

 been found there, but no tin. 1 note, however, as a jxiint of 

 some possible significance, that tourmaline f[uartzites of identical 

 character occur about the contact on the j>roperty of the Good 

 Hope Tin Mines at Kuil's River, and on Papegaaisberg. I have 

 not been able to find the rock in place on Papegaaisberg, but 

 boulders of it are abundant all down the south slope of the hill. 

 The rock is peculiar in appearance, consisting of angular frag- 

 ments oi white ([uartzite in a dense black base of minute tour- 

 maline needles. I have found lx)ulders of this rock as far to 



* •' On Veins and Inclusions in tlie Stellenbosch Granite." Repi. S./1. 

 Ass. for Adv. of Sc. Port Elizabctli (1912). 247-251. 



