ZINC ORES OF THE EDWARDS DISTRICT 39 



are contemporaneous, but in some cases the sulphides are younger 

 than the silicates although, judging from the published descriptions, 

 they follow the sulphides rather closely. 



Similar genetic conditions are shown in the ore deposits of the 

 Suan mining concession, Korea, recently described by Higgins. 1 

 Here again silicates, such as diopside and phlogopite, developed 

 before the sulphides and the latter " replaced the calcite in prefer- 

 ence to the silicates." 



From these examples, whose number might be greatly increased, 

 it is evident that, from the genetic standpoint, the zinc ores of the 

 Edwards district belong to an important and widespread type of 

 deposits, the essential feature of which is their occurrence as replace- 

 ments of limestone- effected through the influence of hot gases and 

 solutions evolved by intruding granitic, or -related, magmas. 



1 Higgins, D. F., Geology and Ore Deposits of the Colbran Contact of the 

 Suan Mining Concession, Korea ; Economic Geology, Vol. XIII, 1918, pp. 



1-34- 



