520 Reviews — Geology and Iron Ores of Cuytma District. 



In a second paper the author gives an account of two new genera 

 of Theropoda ; the bones of various known sj)ecies are also described. 

 Both papers are illustrated by excellent photographic reproductions. 

 ^ F. H. A. M. 



Notes on the Geology and Iron Ores of the Cuyuna District, 

 Minnesota. By E. C. Harder and A. W. Johnston. Bull. 

 660-A, U.S. Geol. Survey, pp. 26, with one map. 1917. 



TN its geological features the recently developed Cuyuna range 

 -*- strongly resembles other iron-producing areas of the Lake 

 Superior region. As elsewhere, the ores belong to the pre-Cambrian 

 and present the same types of ore and country rock. The region 

 is almost entirely covered by a thick mantle of drift, and it is of 

 great interest to find that the discovery of iron-ore was entirely due to 

 the existence of abnormal magnetic conditions. The occurrence of 

 these abnormalities has long been known, but iron-bearing rocks 

 were first proved by boring in 1904, and production began in 1911. 



The rocks of the region, so far as known, are generally considered 

 to be equivalent to the Virginia slate of the Mesabi district, but much 

 more detailed work is required before this correlation can be regarded 

 as proved. They have been invaded, after the principal meta- 

 morphism, by igneous intrusions, supposed to be of Keweenawan age ; 

 here and there are outliers of Keweenawan lavas and of Cretaceous 

 sediments. 



The iron-bearing rocks are folded into a complex series of N.E.- 

 S.W. synclines and anticlines, forming a south-west extension of 

 the Lake Superior synclinorium ; the predominant dips in both 

 limbs of the folds are to the south-east. The ore-bodies are exactly 

 similar in general character to those of other ranges, shoAving a wide 

 variation of type. The best quality yet known, a soft blue haematite 

 from the Croft Mine, runs up to 67 or 68 per cent metallic iron, with 

 very low phosphorus ; the main part of the output consists of ore 

 with 58 to 60 per cent iron and running up to 0"4 or 0*5 per cent 

 phosphorus. 



^ R. H. R.' 



South Australia Department or Mines. Mining Review, No. 31. 

 Adelaide, 1920. 



T^HIS half-yearly volume contains statistics of mineral production 

 -'- in the State for the whole of 1919. The general results appear 

 satisfactory, considering the present industrial conditions. The 

 serious diminution in the output of copper has been to a certain 

 extent counterbalanced by the increase in iron-ore, which, for the 

 first time, takes the leading place in value. 



Among the special reports those of most general interest are the 

 Second Summary Report on the utihzation of Leigh Creek coal 

 and an account of the manganese deposits worked by the Australian 

 Manganese Company at Pernatty, A short account is also given 



