(1) The Ore Deposits of South Africa (2) The Geology of Ore Deposits

Abstract

(1) THE second part of Mr, Johnson's “Ore Deposits of South Africa,” of which the first part was reviewed in NATURE, June 3, 1909, vol. Ixxx., p. 395, deals with the goldfields of the Transvaal. The book is intended for the use of prospectors and students, and consists of brief descriptions of each mining field and of short discussions of the genesis of the ores. It is illustrated with sections of the mines, and outline maps of which the shading is not always clearly explained. The author gives an excellent summary of the arguments for the placer and impregnation theories of the origin of the Rand ores, and says that “judging them on their own evidence the writer would unhesitatingly class 'them as detrital ore deposits” (p. 17). He suspends judgment, however, from the consideration that the gold at Pilgrims' Rest is due to impregnation. The ores at Pilgrims' Rest are.quartz stringers in dolomite and altered dolomite; and they are doubtless of the same origin as those in the 'dolomites of South Dakota, which are strikingly different in all essential characters from the banket of the Rand. Mr. Johnson's remark that the analogy between the ores of Pilgrims' Rest and of the Rand is the strongest argument in favour of the impregnation theory for the banket is not complimentary to the other arguments. The most useful parts of the book are the chapters on the less-known secondary goldfields of the Transvaal.