Bornite and its Relation to Other Sulpho- Minerals. 551 



Enargite Cu B As 2 S 8 



Luzonite Cu As 2 S g 



Famatinite Cu 6 Sb 2 S 8 



Sulvanite Cu e V,S p 



Epigenite Cu" 4 Fe" 3 As 2 S 12 



It is thus evident that all the important sulpho-minerals 

 listed by Groth, with the exception of the sternbergite series, 

 can be made to conform to some one of the above simple 

 general formulas. In the case of the sternbergite minerals it 

 is very doubtful whether these are to be considered as inde- 

 pendent species. We are strongly of the opinion that Groth 

 is right when he intimates that sternbergite, argyropyrite, 

 frieseite, and argentopyrite are probably only argentiferous 

 pyrites. 



The compositions of the various sulpho-minerals may there- 

 fore be referred to the following six general formulas : 



M' x R"' a S„ where y = ~ + 3. (1) 



M' x R'" 4 S y , where y = | + 6. (2) 



M' x R'" 6 S y , where y = - + 9. (3) 



M' x R'" 8 S y , where y = | + 12. (4) 



M' X R' V 2 S V , where y = - + 4. (5) 



M' x R v 2 S y , where y= -+ 5. (6) 



Some Morphotropic- genetic Series. 



As a result of the foregoing considerations, it is now desirable 

 to arrange and study the various progressive chemical series 

 into which the sulpho-minerals may be classified. Several of 

 the more important series of minerals with the general formula 



M'xR'^Sy, where y = — + 3, are the following : 





As 2 S- 



,-PbS Series 



Specific gravity 



Orpiment 





As 2 S 3 



3-5 



Sartorite 





PbAs 2 S 4 



5-39 



Dufrenoysite 

 Guitermanite 





Pb As S 



Pb 3 As„S 6 



5-56 

 5-94 



Jordanite 





PbAsX 



6-393 



Galena PbS 1 '45 



Am. Jour. Sci.— Fourth Series, Vol. XXXVII, No. 222.— June, 1914. 

 38 



