246 . Peniield and Ford — Calaverite. 





Monui 



nent Mine. 



Occurrence No. 2. 



Theory. 



Sp. Gr... 



9-328 



Ratio 



9-388 



Ratio 



AuTe 9 



An 



40-99 



•209 1 ; 

 •016 | 



42-77 



' 217 l-99! 

 •004 f 



44-03 



Ag 



1-74 



0-40 





Te 



[57-25] 



•458 '. 



[56-75] 



"455 



55'97 



Gangue. 



0-02 





0'08 







i nr\-nri 



100-00 100-00 



The ratio of Au + Ag: Te in both analyses is 0*98 : 2*00, or 

 very nearly 1 : 2. The second occurrence approaches very 

 near to a simple gold telluride. the per cent of silver, 0'40, 

 being the smallest thus far recorded in any published analysis 

 of calaverite. The specific gravity determinations are a few 

 tenths higher than generally given ; from the nature of the 

 material, however, and the care exercised in taking them they 

 must be very exact. Of the other occurrences examined crys- 

 tal lographically by us, No. 5, from the Prince Albert Mine, 

 contains 3*23 per cent of silver, as determined by Hillebrand, 

 and the others, occurrences 3 and 4, are probably about like 

 the material from the' Monument Mine, judging from qualita- 

 tive tests. 



In all of his publications on calaverite Grenth describes the 

 mineral, as having a bronze-yellow color. This seems to us 

 misleading, for, although the crystals have at times a yellowish 

 cast, the brightest and best of them are silver-white. Some of 

 the dull crystals examined by us have a gray color, very like 

 that of tarnished silver. 



It is interesting to note the production of gold from the 

 Cripple Creek region, as communicated to us by Mr. T. A. 

 Rickard of Denver. During 1900 the production amounted 

 to 877,972 ounces, valued at $18,147,681, and it is probable 

 that the most of this vast amount was derived from calaverite. 

 It was practically all derived from telluride ores, as very little 

 free gold is found in the district, and that only in the upper- 

 most portions of the veins, near the surface. 



Sheffield Laboratory of Mineralogy and Petrography, 

 Yale University, New Haven, July, 1901. 



