354 GEOLOGICAL SUEVEY OF THE TEREITOEIES. 



possible, and only such fragments that showed a distinct cleavage on 

 all sides were subjected to the tests. Pyrite almost invariably is found 

 associated with this mineral, and the idea suggested itself that the iron 

 might be accounted for in that way. Several trials were made, therefore, 

 without giving any sulphur however. It may be stated here that all 

 the examinations were made of pieces obtained from one specimen. 



This mineral has in its physical characters some resemblance to the 

 Altaite, whicb^ however, contains no iron and about 60 per cent, of lead. 



In the open tube, the assay gives off white fumes of tellurous acid, 

 condensing into colorless drops upon being heated to a high degree. 



Before the blow-pipe on charcoal, with the oxygen-flame, the coal is 

 coated with a white layer some distance from the assay, highly volatile, 

 and near it a grayish-silvery coating is formed, consisting of the vol- 

 atilized and recondensed mineral. After treating the assay on charcoal 

 a little while, it becomes slightly magnetic, melts readily, and volatilizes 

 at a comparatively low temperature. 



When gently warmed with concentrated sulphuric acid, not heated to 

 boiling, the tellurium contained in this mineral imparts to the acid a 

 cherry-red color, more or less intense. Nitric acid aiiects it ; nitro-muri- 

 atic dissolves it. The solution obtained is yellow, owing its color to the 

 presence of iron. 



This species occurs both at the Keel Cloud and Cold Spring mines. 

 If subsequent investigations, with a more ample supply of good material, 

 confirm the result of the above examinations, I shall propose to dis- 

 tinguish this mineral from other tellurets of lead by the name of 

 Henryite, dedicated to Prof. Joseph Henry, director of the Smithsonian 

 Institution. 



No. 2. 



Probably orthorhombic, (no crystals were found from which the 

 crystalline form could be deduced beyond a doubt:) occurring mostly in 

 thin threads and foliated masses. Cleavage perfect ; hardness, 1 to 1.5; 

 luster metallic, splendent ; streak submetallic, dark-gray to black ; color 

 between bright lead-gray and steel-blue 5 opaque ; partly malleable and 

 sectile ; flexible when broken into thin scales. 



In consequence of being obliged to work with very small quantities, 

 it was impossible to make more than a partial quantitative examination, 

 which, however, combined with the qualitative, appears to distinguish 

 this mineral from any known species : 



Au, Ag, . . 



18.82 28.60 per cent. 



while the qualitative analysis revealed yet tellurium, iron, and lead ; of 

 the latter merely a trace, however. An approximate determination of 

 the iron leads me to infer that the formula will be — 



3 Ag Te + (Au Fe) Te 



In this mineral, the percental ratio of Au to Ag is 2:3, while in the 

 mineral nearest related to it, in the Petzite, it is 5 :8; and while Petzite 

 contains on an average 25 per cent, of gold and 40 of silver, these 

 figures are not so high in our mineral. 



In the open tube it gives off tellurous acid, acting like No. 1. Before 

 the blow-pipe in the oxygen-flame, it coats the charcoal white, giving in the 

 reduction flame an impure globule of gold and silver, After being heated 



