Gentli.] 224 [Aug. 21, 



1. Native Tellurium. 



The occurrence at the Red Cloud Mine is fully described by Prof. Sil- 

 liman. I have observed it on several specimens in small, very indistinct 

 crystals, with rounded edges ; also in one splendid cleavage piece, show- 

 a plate of f of an inch in length, and nearly ^ of an inch in width, from 

 which I have obtained a hexagonal cleavage crystal of j^ of an inch in 

 length, and I of an inch in thickness. Generally it is disseminated in 

 tine grains through quartz, cleavage perfect, color tin-white, inclining to 

 gray. 



Associated with sylvanite, altaite and pyrite. 



Without destroying my best specimens, I could not get enough of pure 

 material for analysis. 



3. Tetradymite. 



The sulphurous variety of tetradymite has been observed at several 

 new localities : associated with gold ores in small lead-colored scales at 

 Spaulding Co., Georgia ; also in York District, S. C. ; in quartz from the 

 gravel deposits of Burke and McDowell Counties, N. C. ; in gray quartz 

 with gold at the Montgomery Mine, rfassayampa District, Arizona ; and 

 at the "Uncle Sam's Lode," in Highland District, Montana. At the 

 latter place it is found associated both with quartz and gold, and in 

 dolomite. Part of it is oxydized into montanite. The latter, however, 

 is not in a state of sufficient purity for analysis. That the tellurium is 

 present as telluric acid, and not as tellurous acid, is proved by the large 

 evolution of chloriae, when it is heated with chlorhydric acid.* 



The tetradymite occurs here in considerable quantity, in foliated 

 masses with foliae sometimes | of an inch in width and scaly-granular. 

 Its color is between lead-gray and iron-black. It is often tarnished with 

 pavonine colors. 



The gold, which is often interlaminated with it, shows the striation of 

 the teti'adymite, and is evidently the result of its precipitating action 

 upon the gold in solution, in the same manner as already stated in my 

 notice of the pseudomorphous gold after tetradymite from the White 

 Hall Mine (Amer. Journ. of Science [2] XXVIII., 254). 



It is an interesting fact that the tetradymite from Uncle Sam's Lode 

 contains sulphur as an essential constituent, while that from the gold 

 placers of Highland, which I had received from Mr. Kleinschmidt, and 

 described in the Journal of Science [2] XLV., 316, is free from it. 



My friend Mr. P. Knabe has made some very important observations 

 on this subject, which are contained in his letter, dated Highland, Mon- 



* I notice the following misprints in Dr. Burkart's paper, " Uber das Vorkommen 

 verschiedener Tellur-Minerale In den Vereinigten Staaten yon Nord-Amerika," Leon- 

 hard & Geinitz Neues Jahrbuch derMineralogie, etc., 1873, page 491, line 5 from bottom : 

 Xellursccure instead of Tellurige Scaure, and on page 492, line 15, Tellurige Secure in- 

 stead of Tellursceure. 



