178 Reviews — Mining in South Australia. 



Y. — A E,ETiEW OF Mining Operations in the State of South 

 Australia during the half-year ended June 30, 1917. No. 26. 

 Compiled by Lionel C. E. Gee, S.M. Adelaide, 1917. 



IN addition to the mineral statistics for the half-year this review 

 contains an account of the Government diamond drilling opera- 

 tions, with logs of the bores, an account of several districts where 

 there are mineral deposits which seem worth further prospecting, and 

 an account of several mines which are either closed down or doing 

 little work, with suggestions for their improvement. Among the 

 deposits not yet fully prospected are deposits of apatite and graphite 

 and also a large pyritic quartz lode which is regarded as a possible 

 source of sulphur. 



The apatite deposit is situated at Boolcoomatta Spring and consists 

 of pegmatites occurring in Pre-Cambrian gneisses and schists. The 

 pegmatites are very coarse-grained, containing felspar crj^stals up to 

 6 inches in length and plates of muscovite up to 1 inch in width. 

 There are considerable numbers of veins, of which a fair proportion 

 contain apatite in amounts varying from 5 to 60 per cent. The 

 graphite deposits are situated chiefly in the southern part of Eyre's 

 peninsula and consist of graphite schists in a series of gneisses, 

 schists, and quartzites of Pre-Cambrian age. The outcrops are much 

 weathered and decomposed, so that a fair determination of the flake 

 graphite present cannot be made, but it is suggested that the quality 

 Avill improve in depth when the oxidized ferruginous zone is pene- 

 trated. This deposit is regarded as an important one owing to the 

 present large demand for flake graphite for the manufacture of 

 graphite crucibles. The review shows great enterprise on the part 

 of the Government geologists in seeking out new deposits and in 

 trying to revive those mines which for various reasons have ceased 

 work or are likely to be closed. W. H. W. 



YI. — A New Test of the Subsidence Theory of Coral Reefs. 



By R. A. Daly. Proceedings of the National Academy of 



Sciences, vol. ii, p. 664, 1916. 

 rilHE author points out that during the formation of atolls according 

 J_ to Darwin's theory a concavity or "moat" must have been 

 formed between the up-growing reef and the subsiding island. The 

 filling of this moat, which has never been properly discussed, affords 

 another test of the applicability of the theoiy. The moats have 

 always been completely obliterated and the lagoons are very shallow. 

 The possible source and means of transport of the material required 

 for this filling are discussed in detail by the author. The lagoon 

 floor is generally sandy and not covered by growing coral and other 

 organisms, while the transport of sand by waves and currents can 

 only be small and local. The levelness of the floor is inconsistent 

 with filling by this means. Tlie general conclusion is drawn that 

 the processes mentioned are not adequate to explain the facts; and 

 that existing coral-reefs are new upgrowths from platforms formed 

 previously to and independent of reef-growth. The final preparation 

 of the platform is supposed to have taken place during the Glacial 

 period. It. H. R. 



