PRESIDENTIAL ADDRESS — SECTION B. 69 



Dolomite on the Far East Rand, but the generally superior 

 quality of the coal found farther east, combined with the improved 

 railway facilities, have tended of recent years to diminish the 

 amount of coal mined in the area 



There is little probability of any important coal-bearing 

 areas, other than those known at present, being located within the 

 province. 



Diamonds. — The whole of the Witwatersrand-Ventersdorp 

 Province falls within the Diamond Belt previously defined, and it 

 is not unlikely, therefore, that important pipes and dykes of 

 diamondiferous kimberlite await discovery within it. 



The Karroo Province. 



The Karroo Province, occupied by the sedimentary and 

 igneous rocks of the Karroo system and dykes, sills, and laccolites 

 of dolerite intrusive in them.* is by far the most extensive of 

 the mineral provinces, embracing over one-half of the area of the 

 Union. In the value of its mineral production it is second only 

 to the Wtiwatersrand Province, the supremacy of which it will 

 doubtless eventually rival. 



It is not only the great repository of the fuel-wealth of the 

 country, but includes the most productive section of the Diamond 

 Belt. Apart from coal and diamonds, its mineral products include 

 salt, iron-ore, rock-phosphates, fireclay, and other clays, gannister, 

 building-stone and gypsum. Gold has also been found. f Potential 

 sources of mmeral wealth are natural gas, oil and alum shale, and 

 the magnetic copper-nickel deposits of Griqualand East. 



The Copper-Nickel Deposits of lusisiva, Tahankuln, and 

 l^onki, in Griqualand East. — These deposits are similar in many 

 respects to those of Sudbury in Canada, at the present time the 

 principal source of the world's supply of nickel. The ore-bodies 

 occur J at the lower contacts of great cakes or basin-shaped masses 

 of gabbro-norite, merging downward into picrite§, which have 

 been shown by Du Toit to be the remnants of a vast sill intrusive 

 in the lower division of the Beaufort series. The lower surface 

 of this sill appears to have undulated considerably. The existing 

 gabbro masses represent the parts filling the hollows, the inter- 

 vening dome-like connections having been removed by denudation. 

 The principal ore-minerals are pyrrhotite chalcopyrite and pent- 

 landite, with smaller amounts of bornite and niccolite. Platinum 



* It has also been made to embrace the broad belt of Cretaceous and 

 Tertiary rocks along the coast of Zulnland, and several inliers of Older 

 Granite and rocks belonging to the Transvaal and Waterbera; systems 

 to the south and south-west of Prieska. 



t At Cekkers Kloof, near Cradock, where the gold occurs in asso- 

 ciation with prehnite. 



t Cf. Du Toit, A. L. : The Geology of the Transkei. an Explanation of 

 Sheet 27 (Cape). Geological Survey, Union of South Africa (1917) , 

 18-27. 



§ These rocks represent a special phase of the widespread Karroo 

 dolerite. 



