1874.] ^^'J [Genth. 



The atomic ratios between gold, silver and tellurium, and the com- 

 bined gold and silver and tellurium are as follows : 



a Au 



r " 



Ag 



Te = 1 : 0.96 : 6.98 — (Au Ag) 

 " = 1 : 0.91 : 7.29 — " 

 " =1 : 0.84 : 6.45— " 



6. Calaverite. 



Te = 1 : 3.6 



" =1 : 3.8 

 <' = 1 : 3.5 



I have observed one very minute specimen of this rare mineral amongst 

 those from the Red Cloud Mine, which Mr. Schirmer sent me. It fully 

 answers the description which I have previously given (1. c). 



It is associated with sylvanite and quartz. It contains a somewhat 

 smaller percentage of silver than that from the Stanislaus Mine in Cali- 

 fornia. 



The scarcity of the material did not allow me to obtain for analysis 

 more than 0.1654 grs., from which 0.0050 grs. of quartz were deducted. 

 Dr. G. A. Koenig reduced 0.0333 grs. before the blowpipe, and obtained 

 42. 32 per cent, of gold and silver, which I then separated with the results 

 given below. 



It contains : 



Gold = 40.59 — 39.76 ^ 



Silver = 2.34 — 2.56 j"^^-^^ 



Tellurium = 57.67 — by diflf. :=. 57.68 



Copper and iron = traces 



100.50 100.00 



I was in the hope that I would find in the oxydized specimens of the 

 tellurium ores from the Red Cloud Mine interesting products of decom- 

 position, but observed hardly anything else than native gold, sometimes 

 in very minute scales in the partly decomposed petzite, and small quali- 

 ties of cerargyrite. There is also a minute quantity of what is probably 

 tellurate of silver present, because if the oxydized minerals be treated 

 with ammonic hydrate, and the amnionic solution be filtered and boiled, 

 and subsequently acidulated with nitric acid, the argentic chloride be 

 j)recipitated, the filtrate from this contains both silver and tellurium. 



I also observed among the oxydized pieces, one which had a yellowish 

 coating, probably montanite ; the quantity, however, was too small for 

 any investigation other than a determination of the presence of bismuth 

 and tellurium. 



7. Tellurate op Copper and Lead — a new mineral. 



This new tellurate has been discovered by Mr. P. Kuabe, in the " Iron 

 Rod" Mine, Silver Star District, Montana. He had sent me a small 

 quantity of the same, which consisted of an apparently uniform siskin- 

 green powder. 



