Bornite and its Relation to Other Suljpho- Minerals. 547 







Molecular 





Equiva- 

 lent 









Name of 

 Mineral 



Compo- 

 sition 



Weight, 

 M 



Specific 

 Gravity 



Volume, 

 V 



X 



1> 



u 





Fe 2 S 3 

 Cu„ Fe 2 S 4 



207-91 

 183-56 



4-2 



43-705 



3-5407 



3-5407 





Chalcopyrite 



3-4897 



Barnhardtite 



Cu 4 Fe„S 5 



175-44 



4-521 



38-806 



3-3856 



3-3856 



3-3856 



Bornite 



Cu 6 Fe 2 S 6 



171-39 



4"9 



34-977 



3-2704 



3-2704 



3-2704 



(C 



Cu 8 Fe„S 7 



168-95 











_._ _ 







. 



u 



<X Fe 2 S 8 



167-33 



5-072 



32-989 



3-2072 



3-2072 



3-2072 



it 



Cu lf Fe,S B 



166-17 



5-086 



32-672 



3-1950 



3-1950 



3-1950 



a 



Cu 14 Fe t S 10 



165-40 



5-248 



31-516 



3-1587 



3-1587 



3-1587 



a 



Cu 16 Fe 2 S n 



164-62 















_ _ 







a 



Cu 18 F ei S 12 



164-08 























Chalcocite 



Cu,S 



159-21 



5-51 



28-895 



3-4302 



2-9466 



2-8586 



This table shows that the topical axes, which take into con- 

 sideration not only the elements of crystallization, but also the 

 chemical composition, as expressed by the molecular weights 

 and the specific gravities, show striking similarities. Of the 

 three axes, two, ty and &>, vary quite regularly from their 

 maximum values for Cu 2 Fe 2 S 4 to their minimum for CujS. In 

 the case of %, there is a steady decrease down to Cu 14 Fe 2 S 10 , 

 the last intermediate member for which the axes can be cal- 

 culated, and then an increase to Cu 2 S. This change involves 

 passing from the cubic to the orthorhombic system. These 

 relationships are perhaps brought out a little more clearly in 

 the following, where %', yjr r , and a>' are the values obtained 

 when the topical axis, yjr, corresponding to the b axis of chal- 

 cocite, is taken as the unit for the whole series. 



x 



•V 



Fe 2 S s 

 Chalcopyrite Cu 2 Fe 2 S 4 



Barnhardtite . 



Bo 



nite 



Cu 4 Fe 2 S 5 

 Cu c Fe 2 S 6 

 Cu 8 Fe 2 S 7 

 Cu 10 Fe 2 S 8 

 Cu l2 Fe 2 S 9 

 Cu 14 Fe 2 S, 

 Cu^Fe.S, 

 Cu Fe„S, 



1-2016 

 1-1490 



1-1099 



1-0884 

 1-0843 

 1-0720 



1-2016 

 1-1490 

 1-1099 



1-0884 

 1-0843 

 1-0720 



1-1843 

 1-1490 

 1-1099 



1-0884 

 1-0843 

 1-0720 



Chalcocite Cu„S 



1-1644 



1-0000 



0-9702 



The topical axes show, therefore, progressive changes which, 

 as far as can be determined from the very meager data con- 

 cerning the specific gravities available at present, are fully in 



