416 Koenig — J^evj Species Melanochalcite and Keweenawite, 



with HKO3, the heterogeneous nature becomes visible even to 

 the naked eye. 



Two fragments gave : 



Cu = 92-78 

 As = 5-85 



Cu = 93-96 

 As = 5-74 



1-4755 

 0-0765 



Cu: As = 18-8 : 1 

 Cu : As = 19-3 : 1 



98-63 99-70 



Two other fragments were detached close to the one whose 

 composition has just been given. 

 They gave : 



Cu =z 96-2 and 94-5 



As = 3-8 5' 5 (by difference) 



100-0 100-0 



Here the ratios are Cu : As=30-1 : 1 and 25*5 : 1. The figures 

 show plainly that definite proportions cannot be looked for ; 

 but they indicate, as I look at it, that we must assume here 

 conditions similar to those of pig iron, or of alloys. Further 

 studies may give better light, especially in the direction of 

 etching. In speaking of such alloys as these (^, A), I ven- 

 ture to propose the word " Semi- Whitney ite,^'' to be used like 

 Mohawk- Whitneyite, or Mohawk- Algodonite, meaning neither 

 a species nor a variety ; in the sense of a rock rather than of a 

 mineral. 



Chemical Laboratory, Michigan College of Mines, 

 Houghton, Mich. 



