W. H. Hobbs — Goldschmidtite, a New Mineral. 359 



Percentage composition. Eatio. 



Au 31*41 '1596 ■ 



Ag.. 895 "0831 



Te (59-64) -4*771 



100-00 



These proportions correspond almost exactly with the 

 formula An 2 AgTe 6 , and show that the mineral is a new species, 

 which I propose to call Goldschmidtite, in honor of my friend, 

 Professor Victor Goldschmidt, of Heidelberg, the inventor 

 of the two-circle goniometer and the author of Index der 

 Krystallformen and WtnJceltabellen. 



Below are given in parallel columns the estimated and the 

 theoretical proportions of the constituents of this mineral on 

 the basis of the formula An 2 AgTe 6 : 



Calculated. 



Te (59-64) 59-95 



Au 31-41 31-44 



As: ... 8-95 8-61 



100-00 100-00 



Relationships with other Tellurides of Gold and Silver. 



, . The mineral sylvanite contains the same elements as Gold- 

 schmidtite but in the proportions represented by the formula 

 AuAgTe 4 .* The mineral calaverite differs in being richer in 

 gold and is not generally credited with a definite formula, 

 because of slight variations noted in the content of silver. 

 The number of analyses of this mineral which have now been 

 made renders it possible, as it seems to me, to arrive at a more 

 definite formula than (Au,Ag)Te 5 , which assumes an isomorph- 

 ous relation between gold and silver in the compound that 

 does not exist so far as we know. Comparison of the analyses 

 of calaverite which are given below brings out their striking 

 uniformity with the exception of the silver percentage, and 

 this would seem to indicate that a mineral corresponding to the 

 one having the highest silver percentage (3*52) may form iso- 

 morphous mixtures with one that is richer in gold or perhaps 

 entirely free from silver. Since, however, a large proportion 

 of the analyses contain silver in amounts approximating the 

 maximum percentage, it is improbable that isomorphous mix- 

 tures occur with tellurides much richer in silver. The formula 

 Au 9 Ag|Te 21 seems best to represent the composition of this 

 mineral. 



* Groth, Tabellarische Uebersicht der Mineralien, 4te Auflage, Braunschweig, 

 1898, p. 28. 



