240 ECONOMIC GEOLOGY 



First magnetite, then pyrite and gangue, then pyrrhotite. The 

 mass is then fractured and in the cracks there appears pentlandite. 

 These ores are all fractured and in the cracks thus formed 

 chalcopyrite is deposited. 



According to F. W. Voit the nickel ores of Dobschau, Hungary, 

 were deposited from solution in a gangue of calcite at or near 

 contacts of diorite. C. R. Keyes considers the nickel mineral, 

 linnseite at Mine La Motte, Mo., of secondary origin. It 

 occurs in limestones as a metasomatic replacement deposit with 

 lead and copper. 



FIG. 120. Roast yards near Victoria mine, Mond Nickel Company, 

 Sudbury district, Ontario. (After A. E. Barlow, Canadian Geological 

 Survey.) 



The famous Temiskaming mining district in Ontario was dis- 

 covered in 1903. The sulphides and arsenides of nickel and co- 

 balt were all formed through solutions from heated waters asso- 

 ciated with the basic intrusives of post-Middle-Huronian age. 

 The native silver of Cobalt and Gowganda was the last mineral 

 to form from solution in the ore bodies for it cuts the smaltite 

 and the gangue mineral calcite. According to W. G. Miller 

 these deposits are analogous to those of Annaberg, Saxony, and 

 Joachimsthal, Bohemia. The ores may represent a leaching of 

 the accompanying basic eruptive rocks, or they may have been 



