Pearceite and Polybasite. 41 



5. Drumlummou mine, Marysville, Montana, crystals, Penfield 

 (analysis by Knight), this Journal, ii, 18, 1896. • 



6. Same analysis as 5 with the -42 per cent of insoluble matter 

 distributed proportionately. 



7. Veta Rica mine, Sierra Mojada, Mexico, crystals, Van Horn 

 and Cook (analysis by Dubois), this Journal, xxxi, 523, 1911. 





l 



2 



3 



4 



5 



6 



7 



s 



16-83 



17-07 



18-13 



17-73 



17-71 



17-78 



17-46 



As 



6-23 



7-29 



7-01 



6-29 



7-39 



7-43 



7-56 



Sb .... 



0-25 



0-43 



0-30 



0-18 













Ag 



72-43 



6354 



56-90 



59-73 



55-17 



55-40 



59-22 



Cu.... 



3-04 



10-70 



14-85 



12-91 



18-11 



18-19 



15-65 



Fe . . . . 



0-33 



0-60 









1-05 



1-05 







Zn .... 



0-59 



.... 



2-81 



3-16 







w - - - 







Insol. . . 



99-70 



99-63 



100-00 







0-42 

 99-85 



99-85 









100-00 



99-89 











5-92 



6-125 







Sp. g. . 





6-33 



5-94 



6-10 



6-166 





6-067 









(recal.) (recal.) 









A comparison of the analyses shows that the two most recent 

 ones, 6 and 7, are most similar in chemical composition, both 

 being the pure arsenical molecule. However there was no iron 

 in 7. The analysis resembling 6 and 7 most closely is 2. It is 

 also significant that these three analyses were made from pure 

 crystallized mineral, while 3 and 4 were made from material so 

 impure that 12-81 and 28 - 18 per cent had to be deducted for 

 impurities, and the result recalculated before it could be 

 expressed in the form given above. Furthermore it was 

 stated that there was 046 and 2-57 per cent of FeC0 3 in 3 and 

 4 respectively, and although some siderite may have been visi- 

 ble, it seems plausible that some iron should be credited to the 

 mineral, since that element is fairly constant in most pearceite 

 as well as polybasite. It is not certain what kind of material 

 Rose used in 1, although Hintze* mentions under polybasite 

 "trigonal gestreifte Krystalle (Rose's Analyse vergl. S. 1169) 

 iri Quarz-Drusen, sowie blattrige bis schalige Massen, mit 

 Pyrargyrit, Silberglanz, Eisenkies, brauner und gelber Blende." 

 It is to be noted that the specific gravity was not determined, 

 and that none of the undoubtedly crystallized material given 

 in 2, 6', and 7 contains zinc. The first five analyses given above 

 were recalculated in order to find their combining ratios. In 

 doing this the International Atomic Weights for 1911 were 

 employed with the following values : S, 32-07 ; As, 74-96 ; 

 * Op. cit. page 1173. 



