MANGANESE IN THE CAPE COLON V. 201 



forming impregnations of tlie granite, most likely after the latter 

 had been somewhat decomposed and rendered porous. This 

 can be observed on both sides of the hill known as Little Lion's 

 Head, in the granite forming the base of the hill. At other spots 

 where the granite is fresher the impregnations are wanting, but 

 crack fillings are noticed. 



An interesting occurrence is noticed on the slopes of Devil's 

 Peak (Cape Town). In the surface soil, which is known to be 

 imderlain by Malmesbury Slates, there is an outcrop of a quartz 

 reef, the country slate being quite hidden by the soil. This 

 quartz has all its cracks and crevices filled with manganese ore — 

 essentially a secondary deposit. The course of this reef will not 

 necessarily coincide with that of the manganese lode, which I 

 am of opinion will be found to be similar to the impregnations 

 observed in the granite. 



The more important lodes in the Table Mountain Sandstone 

 are rather irregular in their occurrence. They form approxi- 

 mately vertical bodies of ore of very varying richness, this 

 depending on the size of the apertures through which the original 

 solutions passed. A large proportion of the ore is simply sand- 

 stone stained black, but this is easily distinguishable from the 

 good ore. Consequently, though owing to the nature of the 

 occurrence of the ore a very large amount of hand sorting is 

 necessary; this can be easily carried out, even by natives. 



It will be interesting to note how the composition of the ore 

 varies at different localities. From time to time samples have 

 been sent to Cape Town to be analysed. Formerly, when manu- 

 ganic dioxide was the only important constituent of manganese 

 ore, which was used only for the preparation of chlorine, the 

 results of the analyses showed percentages of manganic dioxide 

 and manganous oxide. Later, when the ore was used for steel- 

 making the analyses showed percentages of metallic manganese. 

 Quite recently another use has been discovered for the ore, 

 namely, the manufacture of a paint, which is claimed to possess 

 superior qualities to those of other paints. In this case the 

 percentage of neither manganese nor oxygen is of so much 

 imix)rtance as the physical condition of the ore. The recent dis- 

 coveries made on Devil's Peak are being put to this use. 



A sample of ore from Ilout Bay analysed in 1894 showed 

 80 per cent, of manganic dioxide, 5 per cent, of manganous 

 oxide, and 9 per cent, of oxide of iron, besides other impurities. 

 Another from Constantia showed 8=, per cent., 12 per cent., and 

 nil respectively. These must be considered as good ores both 

 as regards manganese and oxygen contents, but unfortunately all 

 the ores analysed do not .show smiilarly good results. Samples 

 from many localities have been examined, varying in manganese 

 contents from 50 per cent, to next to nothing, but it is impossible 

 to say if these samples were rei)resentative of the deposits from 

 which they were taken. 



