284 Reviews — Secondary Enrichment in Copper Ore. 



question of the origin of the ironstones of the Lake Superior 

 region. The chief mineral product of the district is gold, 

 which occurs both in quartz lodes and in replacement deposits of 

 auriferous sulphides in fissured dissemination-zones. Antimonite 

 lodes are known to exist, and scheelite has also lately been produced 

 from quartz veins in felsite on the Scheelite King claim, and as 

 a by-product from several gold-mines. 



R, H. R. 



XV. — Microscopic Secondary Sulphide Enrichment in the 

 " Kuromono " Ore from the Kosaka Mine in the Province 

 of lliKucHU, Japan. By Takeo Kato. Journ. Geol. Soc. 

 Tokyo, vol. xxv, pp. 7, with plate, 1918. 



fTlHIS is a study of the details of secondary enrichment seen on 

 X microscopic examination of a mixed pyrite-chalcopyrite-galena- 

 blende ore. The secondary copper minerals observed are bornite, 

 chalcocite, and covellite : these occur enclosed in chalcopyrite and 

 are formed by metasoraatic alteration of pyrite and chalcopyrite by 

 descending solutions from the zone of oxidation above. The careful 

 drawings reproduced in the plate are of considerable interest as 

 showing clearly the order of formation of the different minerals 

 and especially the development of bornite from chalcocite, a reversal 

 of the usual order. Pyrite enclosed in blende has also been altered 

 successively to bornite and covellite. 



XVI. — The Ring-ore from the Akenobe Mine, Province of 

 Tajima, Japan. By Takeo Kato. Journ. Geol. Soc. Tokyo, 

 vol. xxiv, pp. 35-41, with plate and 2 text-figures, 1918. 



rpHE author describes concentric growths of ore and gangue 

 JL minerals round fragments of silicified country rock in veins. 

 The successive layers consist of (a) quartz with cassiterite, (b) 

 chalcedony, (c) quartz. The interspaces contain fluorspar, scheelite, 

 and siderite, and the whole is cut by numerous vein lets of 

 chalcopyrite, forming a tin-copper ore. It is supposed that the 

 second layer was deposited as gelatinous silica and afterwards 

 recrystallized as fibrous chalcedony ; this suggests that the veins 

 were formed hydrothermally at a temperature below the critical 

 temperature of water. 



XVII. — Pre-Histort in Essex, as recorded in the Journal of the 

 Essex Field Club. By S. Hazzledine Warren, F.Gr.S. pp. 44. 

 Stratford and London, 1918. 

 ~R. HAZZLEDINE WARREN" has performed a useful service 

 by bringing together in this publication a bibliography, with 

 brief abstracts in most cases, of the papers dealing with prehistoric 

 archaeology in the widest sense, to be found in the Journal of the 

 Essex Field Club. It covers a very wide range of subjects from the 

 problem of pre-palseolithic man and the relation of palaeolithic and 

 glacial deposits to salt-making, wild-fowl decoys, and folklore, 

 and cannot fail to be of great value to workers in this field of 

 research. 



