28 Mineralizers in Ore Segregations [226 



great many occurrences, which numerous authors consider a 

 direct segregation from eruptive rocks, one must at least con- 

 sider probable a later secondary recrystallization of the ores 

 by aqueous processes which brought about a partial migration 

 and an impregnation of the wallrock." These conclusions 

 are based largely on his own work in 1902 and 1903 on the 

 deposits of nickeliferous pyrrhotite and chalcopyrite at Soh- 

 land in Saxony, where he found ore deposition took place by 

 replacement subsequent to the hydrothermal alteration of the 

 rock, though he believes both followed immediately after its 

 solidification. 



"With the exception of the treatment of the sulphidic ores, 

 the position of Beyschlag, Krusch and Vogt is similar to that 

 taken by Beck. Their ideas are of course largely those devel- 

 oped by Vogt. Their conception of the genesis of these ore 

 deposits is that, " In the same manner in which larger masses 

 of mica and feldspar can collect out of a granite magma, 

 segregation of ores can take place, as for example of mag- 

 netite, titaniferous magnetite, chromite and pyrrhotite, in 

 such igneous rocks which normally carry these ores as acces- 

 sory constituents." They call attention to the fact that the 

 ore minerals followed by the iron-magnesium silicates are 

 the earliest constituents to crystallize in most eruptive rocks 

 and they are also the constituents that migrate in magmatic 

 differentiation. Magmatic segregation is distinguished from 

 ore deposition in which mineralizers participate as follows: 

 " The genetic difference consists essentially therein that the 

 magmatic segregations result from a single differentiation 

 process of the magma, whereas in the case of the pneumato- 

 lytic and contact metamorphic deposits the metallic content 

 originally belonging to the magma is transferred to an aque- 

 ous or gaseous solution and later deposited from this through 

 new processes." Though in most cases the two groups are 

 considered as sharply differentiated, they admit that occa- 

 sionally there are intermediate stages in which magmatic dif- 

 ferentiation is accompanied by pneumatblytic or pneumato- 

 hydatogenetic processes. They definitely state that the chrome 



