THE TELLURIDE ORES. 1123 



even for silver fluoride, which, according to Lenher, acts upon gold chloride 

 as follows: 



AuCl 3 - r 3AgF- r 3H 2 0=3AgCl+Au(OH) 3 - r -3HF 



Lenher's work suggests the advisability of experimenting as to the effect 

 of the soluble fluorides and of hydrofluoric acid upon solutious bearing chlo- 

 rides of both gold and tellurium. In this or some other combination of the 

 three elements gold, tellurium, and fluorine with perhaps other compounds 

 may lie the key to the problem of the precipitation of the gold tellurides. 



The abundant fluorite associated with the tellurides has frequently 

 been cited as evidence of pneumatolitic action in connection with such 

 deposits. But Penrose's description of the Cripple Creek ores gives no 

 support to this hypothesis. All his descriptions show the phenomena to 

 be those which, in many other districts, are well known to be due to water 

 solutions. For instance, the most abundant gangue mineral of the district 

 is silica in quartzose, chalcedonic, and amorphous forms. It is well known 

 that these compounds are the most abundant ones deposited by under- 

 ground water. Others of the more abundant gangue minerals are oxides 

 of manganese, calcite, gypsum, barite and kaolin." 



Furthermore, in some of the mines, as the Gold Coin mine, the ore 

 of which is in granite, there has been solution of biotite, quartz, and 

 feldspar, and this can not be attributed to pneumatolitic action. 6 



I therefore find no evidence of pneumatolitic action in connection with 

 the genesis of the telluride ores. It is uncertain what conditions produce a 

 somewhat homogeneous compound consisting of definite proportions of 

 silver, gold, and tellurium, as in the telluride minerals. Doctor Lenher has 

 been at work on this problem for some time, but as yet without determin- 

 ative results. He has treated gold solutions with hj^drogen telluride and 

 has worked on the various tellurium compounds, such as the chloride, 

 bromide, fluoride, and alkaline tellurites, all experiments being made in the 

 presence of a reducing agent, such as sulphurous acid; yet in no case has he 

 been able to get homogeneous compounds of gold and tellurium, but, on the 

 contrary, has obtained metallic gold and tellurium salts, or mixtures of 

 gold and tellurium of irrational composition. While the problems of the 



£ : 



"Penrose, cit., pp. 123-129. 



'j Penrose, R. A. F., jr., Mining geology of the Cripple Creek district: Sixteenth Ann. Kept. U". S. 

 Ceol. Survey, pt. 2, 1895, pp. 159-161. 



