J. W. Richards — " Mohawkite" 457 



Art. XXXVIIL— " Mohawkite" ; by Joseph W. Bichards. 



Dr. Koenig has given the name Mohawkite to the nickel- 

 iferous and cobaltiferous variety of domeykite found at the 

 Mohawk mine. He bases this oh his analyses, corresponding 

 to (Cu,Ni,Co) 3 As.* 



Dr. Ledoux published the results of an analysis of a mineral 

 from the same mine,f which corresponded closely to (Cu,N"i a 

 Co) 4 As, and which he proposed should be called Mohawkite. 

 Dr. Koenig, however, throws doubt upon the formula obtained 

 by Ledoux ; also claims that if Cu 4 As does exist, a new name 

 must be found for it, as he has preempted the name Mohawkite 

 for his variety of domeykite. The object of this communica- 

 tion is to substantiate Ledoux's analysis and formula, and 

 thereby prove the existence of the new species (Cu,lS"i,Co) 4 As. 



Last autumn the writer received from Foote, of Philadelphia, 

 a specimen from the Mohawk mine marked " Mohawkite ?" 

 Analysis of the material, completely freed from gangue, gave 



Copper 70-8$ 



Cobalt. r . 6-4 



Nickel trace 



Iron 0-0 



Arsenic (by difference) 22*8 



100-0 



The atomic ratios from the above are 

 Copper 



Cobalt 



Arsenic 



^ 8 = 1-117 ' 



63-4 



6-4 



— = 0-108 



59 



,1-225 



22-8 



= 0-304 



75 



1-225 



- 4-003 



and the formula 



0-304 



Hence the atomic ratio. 



(Cu,Co,Ni) 4 As. 

 Dr. Ledoux's analysis, as calculated by Koenig, gives the 



1 '228 



corresponding atomic ratio — = 4*066. Koenig, however, 



makes a slight mistake in adding the basic valences, and the 



*This Journal, December, 1900. Zeitschr. fur Krystallographie und Miner- 

 alogie, xxxiv, 70 (1901). 



f Engineering and Mining Journal, April 7, 1900. 



