NATURE 



\% 



THURSDAY, AUGUST 6, 1903. 



THE MINERAL WEALTH OF AFRICA. 

 Les Richesses Minirales de I'Afrique. By L. de 

 Launay. Pp. 395 ; with 71 figures and maps. 

 (Paris : Ch. B^rangfer, 1903.) Price 20 francs. 



PROF. DE LAUNAY gives a further proof of his 

 indefatigable industry in this new volume from 

 his pen. It is a formidable task to deal even briefly 

 with the mineral wealth of a huge continent, which 

 has been only imperfectly explored ; but fortunately 

 the author is eminently qualified for the task. He is 

 no novice in writing upon mineral deposits, and he 

 has visited many mines in North Africa, besides the 

 most important districts in the south. The book is 

 arranged so as to suit two classes of readers, those 

 who wish to learn all they can about the occurrence 

 of some given mineral, such as gold, copper ore, 

 phosphate of lime, &c., and those whose interest re- 

 lates only to some particular country or region. This 

 arrangement involves a certain amount of duplica- 

 tion, but it is certainly a convenience. Thanks are 

 likewise due to the author for his little sketch maps. 

 Who has not experienced the want of such maps? 

 For when seated in an easy chair the reader is apt 

 to be too lazy to get up and fetch his atlas, and he 

 consequently often fails to derive full benefit from the 

 work he is perusing. 



What is the mineral wealth of South Africa? Of 

 the future mineral resources of the Dark Continent 

 we are ignorant; further explorations may reveal 

 new treasures; but if by " mineral wealth " is under- 

 stood the value of the present output, the question is 

 answered by the following tables, which have been 

 compiled from the Blue-books published annually by 

 the Home Office. Though the information is neces- 

 sarily incomplete, it will suffice for the purposes of 

 the present article. 



In a normal year, such as 1898, gold is seen to be 

 far ahead of any other mineral as regards value ; and 

 when we consider that before the war with the Boers 

 Africa was furnishing more than one quarter of the 

 world's supply of the precious metal, it is evident that 

 Prof, de Launay is fully justified in devoting his first 

 chapter to a description of the auriferous deposits of 

 the continent. The gold mines of the Witwatersrand 

 naturally claim a full share of attention. Excellent 

 figures, with full descriptions, explain the nature of 

 the " banket " or gold-bearing conglomerate, and the 

 question of the origin of the gold is discussed at some 

 length. The three usual hypotheses are brought for- 

 ward; they may be spoken of briefly as "previous 

 origin," "contemporaneous origin," and "subse- 

 quent origin." In other words, it is supposed by 

 some geologists that the gold is a detrital product, 

 like the pebbles of quartz; others suggest that it was 

 deposited from solutions while the pebbles were find- 

 ing a resting place; whilst most mining engineers 

 favour the idea that solutions brought it into the 

 conglomerates long after their consolidation. The 

 pros and cons are given in each case; however, there 

 are difficulties in accepting any one of the three 

 NO. 1762, VOL. 68] 



theories advanced, and Prof.' de Launay honestly 

 confesses that he is puzzled, and that he cannot make 

 up his mind on the matter. 



He is careful to point out that the Rand must be 

 regarded as an exceptional case, and that it by no 

 means follows from the discovery of " banket " in 

 West Africa that the " Jungle " gold mines, as they 

 are known on the Stock Exchange, will necessarily 

 prove to be rich and valuable properties. 



The pages relating to the occurrence of gold in 

 Egypt contain matter of much antiquarian interest; 

 the public are only now beginning to learn that 

 Egypt was the California of the Old World, and' 

 that gold w^as being extracted from quartz veins 

 between the Nile and the Red Sea at least 2500 years 

 B.C. But the author makes a mistake in saying that 

 the gold occurs under conditions similar to those 

 under which it is found in Cornwall. In that county 

 we have no auriferous deposits, for the small grains 

 of the precious metal occasionally found in working 

 stream tin in olden days were, practically speaking, 

 mineralogical curiosities. 



Next in importance come diamonds ; for though the 

 emeralds of Gebel Sahara and the turquoises of Sinai 

 were known and worked by the ancients, the only 

 gem-mining which need be taken- into consideration 

 at the present time is that of South Africa. It is 

 a curious fact, on a continent in which both gold 

 and gems were obtained in considerable quantities 

 even in very remote ages, that the deposits which 

 are now yielding so lavishly should have remained 

 undiscovered until the latter part of the last century. 

 The mode of occurrence of diamonds in South Africa 

 is thoroughly well known to geologists ; but the pre- 

 cise manner in vt'hich they were originally formed 

 still affords room for speculation. Prof, de Launay 

 repeats the hypothesis, already suggested in his 

 previous work, " Les Diamants du Cap," that a bath 

 of supercarburetted molten iron and magnesium 

 existed beneath the granite, and that the diamonds 

 were formed on a large scale after the fashion of 

 the minute ones obtained artificially by Moissan. 



The discovery of workable deposits of phosphate 

 of lime is one of recent date; it now appears that 

 they extend more or less continuously from Morocco 

 to Egypt. Algeria already produces more than 

 300,000 tons a year, and Tunisia more than 200,000 

 tons from strata of Eocene age. The Egyptian de- 

 posits, which occur in Upper Cretaceous rocks, are 

 extensive but poor. 



There are reasons for believing that the dry Sahara 

 and Algeria may contain deposits of nitrate of potash 

 and nitrate of soda similar to the " caliche " of Chili; 

 the matter is now being investigated officially. 



Practically speaking, all the copper of Africa comes 

 from Namaqualand; the advent of better means ot 

 transport may render this statement incorrect in the 

 course of a few years, for ores of the metal are known 

 to exist in many parts of the continent. 



Coal of Permo-triassic age is worked in the Trans- 

 vaal, Natal, and Cape Colony, and Rhodesia will 

 scon become a producer. 



The total value of all the minerals produced in , 



P 



