498 schaller: identity of empressite with muthmannite 



Empressite is "massive in structure, careful inquiries having 

 failed to locate any material showing crystal faces. The mineral 

 occurs in very fine granular and compact masses associated with 

 galena and native tellurium." Its properties could therefore be 

 only partly determined. The following compilation of the pub- 

 ished properties of empressite and muthmannite shows their 

 relationship. 



EMPRESSITE 



MUTHMANNITE 



Structure. 

 Color 



Streak. . . . 

 Cleavage. . 

 Hardness. 

 Solubility. 



Formula. . 



Massive 



Pale bronze^ 



Grayish black to black 

 Not determined 

 3. - 3.5 



Readily sol. in hot di- 

 lute HNO3 

 AgTe 



Platy elongated crystals, not 



measurable 

 Very light brass yellow- to 



grayish white' 

 Iron gray. 



Good, parallel elongation 

 2-2+ 

 Decomposed by HNO3, gold 



separating 

 (Ag, Au)Te 



1. On fracture surfaces. 



2. On the exposed surface. 



3. On fresh cleavage surfaces. 



All three analyses of muthmannite, as given by Zambonini, 

 show considerable gold, but in every one the silver predominates 

 molecularly. In Zambonini' s analysis, the ratio of gold to silver 

 is 116 to 244; the gold forms less than one-third of the bases. 



The following are the published analyses of muthmannite, the 

 last three being quoted by Zambonini. 



Analyses op Muthmannite 



