ORIGIN OF ORE DEPOSITS 



45 



magnetites of Constantino, North Africa, noted for tln-ir remark- 

 able freedom from sulphur and phosphorus. 



The /inc-manganese mineral franklinite at Franklin Furnace, 

 N. J., occurs in a metamorphosed limestone with zincite, wil- 

 Irmite and rhodochrosite. 



Corundum, ruby, sapphire and emery occur in the metamor- 

 phosed schists and limestones. The famous emery deposits on 



FIG. 34. Map of the district of Persberg, showing the association of 

 the ore with metamorphosed calcareous rocks. (After Sjorgren.) 



the Island of Naxos in the Grecian Archipelago occur in a meta- 

 morphosed limestone. Metamorphic ore deposits may be recog- 

 nized by their associated minerals and their mode of occurrence. 

 Metamorphic contact deposits are not distributed over large 

 areas but rather confined within the metamorphic aureole in 

 which the change has been effected through the influence of 

 some intrusive. 

 The changes produced in an ore body are along the lines of de- 



