PRESIDENTIAL ADDRESS — SECTION B. 65 



been devised. When one or the other of the processes has been 

 successfully applied, there should be a big increase in the output. 



There is also a small deposit of the more valuable calcium 

 phosphate or phosphorite in the neighbourhood of Saldanha Bay 

 on the Hoetjes Bay Peninsula, and this encourages the belief 

 that further deposits of phosphorite remain to be discovered in 

 this locality or along some other section of the littoral. As the 

 soils of the Union are, generally speaking, very deficient in phos- 

 phorus, any discovery of this nature would be of the utmost 

 importance. 



Another source of rock phosphate investigated by Du Toit* 

 are the phosphatic nodules occurring in the Upper Ecca shales in 

 the Weenen area and other localities in Natal. These contain 

 from 20 to 30 per cent, of phosphoric acid, and have been proved 

 experimentally to have considerable fertilising value when finely 

 ground. 



( )wing to their irregular and sparing distribution through 

 the shale, operations will perforce have to be confined to the mere 

 collecting of the nodules set free by weathering or still partially 

 imbedded in the matrix. Du Toit is of opinion that there is 

 enough of this material scattered over the Weenen area to enable 

 a mill to operate with a small output for some time. With the 

 experience gained it is suggested that other localities, such as the 

 neighbourhood of Tadysmith, might with advantage be investi- 

 gated. 



Chert. 



Chert, suitable for lining tube-mills, has a wide distribution 

 in the Dolomite formation, and is won in the neighbourhood of 

 Frederikstad. in the Potchefstroom district of the Transvaal. 

 Owing to the introduction pf steel and composite liners, the 

 demand has fallen considerably, the output for 191 7 having 

 amounted tO' only 180 tons against 604 tons in 1913. 



Gypsum. 



This mineral is principally used in South Africa in the manu- 

 facture of Portland cement, in which it acts as a retarder. 



There are important deposits at Ngbevu, in the Tugela 

 Valley, in Natal, on the farm Vrede, in the Boshof district of the 

 Orange Free State, and on the farm Bestpan, near Kimberley. 



The demand for gypsum is limited, and there is no likelihood 

 of any great increase in production in the near future. 



Kieselguhr. 



Kieselguhr occurs as an earthy deposit in the beds of certain 

 pans in the Amsterdam district of the Transvaal ; also near 

 Krugersdorp, and in Griqualand West. 



* Cf. Du Toit, A. L. : The Ecca Prosphates of Natal. S.A. Journ. 

 Industries, January, 1918. 



