NATURAL SCIENCES OP PHILADELPHIA. 113 



Old Formula. New Formula. 



(Antimonial.) Tetraheclrite. 



4CUS + SKS3 (CuJ"=S,"=Sb^ S" Sb^=S,"=(Cu.J" 



(Cu,),"Sb,S, 

 (Arsenical.) Tetrahedrite. 



4CuS + As,S3 (Cu;;"=S.,"=As^ S" As^=S,"=(Cu,)'' 



II II 



S" S" 



(Cu,),"As,S, 



Witticbenite. 



3CU3S + BI3S3 S"= Bi"^ S" (Cu.,)/^= 



= S3"=Bi"^ 



(Cu,),"Bi,/"S." 

 Note. Dana gives the atomic ratio of Cu : Bi : S : : 3 : 1 : 3. From his 

 seventh record of analysis (by Schneider), however, this ratio is 4 : 2 : 5. 



Stromej-erite. 

 (Ag,Cu,)S (Cu,)"=S,"=Ag./ 



((Cu,)"Ag./)S," 

 Note. The atomic ratio expressed in Dana's formula is Ag : Cu : S : : 

 1 : 2 : 1, whereas from Stromeyer's analysis it appears very clearly as 1 : 1 : 1. 



Dufrenite. 

 Karsten's Analysis D2. 



I I 



0"=Fe.7^ = 03"EEEP^=0"J 



Libetbenite. 



4CuO.P03-{-HO From tbe atomic ratio. 



Cu : P : II : : : 2 : 1 : 1 : 5 



Cn,"=^0^ = P^ 0" IP 

 (HCu,")(P^O,")'' 

 Olivenite. 

 4CuO.(P,As)0,+ H,p ((H^CiOAs^O,"), 



Cn./^^0,=As^ 6" H' 

 Note. Some P replaces As. 



