ECONOMIC GEOLOGY 473 



that all the gold came from the mountains is improbable, 

 for the metal undoubtedly exists in pyrites enclosed in 

 the Beaufort sandstone. 



Iron. The iron ores of Cape Colony form almost in- 

 exhaustible deposits, but, owing to their geographical 

 situation, are not likely to be worked for many years to 

 come. 



The formation is that facies of the Lower Griqua 

 Town beds known as the Blink Klip breccia described 

 on page 91 and forming two prominent belts striking 

 northwards from near Postmasburg in Hay into the 

 Kuruman Division. As already stated, it has been 

 formed by the solution of the limestone underlying the 

 banded ironstones, the fracturing of the latter, and the 

 replacement of silica by haematite due to circulating 

 waters. The formation varies from banded ferruginous 

 rocks up to masses of pure haematite, and the amount 

 of ore in existence must be enormous. Sedimentary 

 rocks with large percentages of iron occur in the Mary- 

 dale beds, Kraaipan beds, and the Lower Griqua Town 

 beds from Prieska up to Bechuanaland ; it is unknown 

 at present whether the iron oxides are ever locally con- 

 centrated in these beds in other places than those 

 occupied by the Blink Klip breccia. 



Lead and Silver. 'Galena, sometimes rich in silver, is 

 known to occur in veins in the Campbell Kand lime- 

 stone at several localities on the Kaap Plateau and also 

 in the Griqua Town jaspers near Witwater, Hay. 

 Argentiferous galena was found many years ago at the 

 Maitland mines a little to the west of Port Elisabeth. 



