Koenig — New Species Melanochalcite and Keweenawite. 413 



I give the specific gravity (1. c.) as 7*71, the calculated specific 

 gravity as7'75, whilst the keweenawite gives the gravity 7"681, 

 which is very close indeed. Nickel and cobalt having nearly 

 the same specific gravities and not much different from copper, 

 this slight difference is readily accounted for. 



3. Mohawkite and Domeykite. 



During the past year I have made several more analyses of 

 these two minerals from the Mohawk mine. The material 

 was in part collected by me on the spot or sent to me by Mr. 

 Fred Smith, to whom I wish to express my indebtedness. 



The colors of these minerals seem alike to those of the 

 fabled chameleon, and the identification by the eye is made 

 very difficult, in fact impossible. 



a. The mineral appears in form of large masses in calcite 

 with a color equaling that of chalcopyrite ; altogether unlike 

 any previously seen domeykite or mohawkite. Mr. Smith 

 states that it had this yellow color when it came up the shaft. 

 It is exceedingly brittle, crumbling between fingers into blue 

 and purple fragments. B. B. shows trace of cobalt and trace 

 of antimony. 



Cu = 70-56 

 As = 29-50 



It is therefore domeykite. 



h. Large iron gray mass, looks like arsenopyrite. B. B. gives 

 strong cobalt reaction. 



Cu = 6V-86 



Ni + Co = 3-32 

 As =z 28-10 



99-28 



The mineral proves to be mohawkite ^ but the sum of cobalt 

 and nickel is only one-third of that in my original mohawkite. 



c. Mr. Knight, one of my students, picked up a specimen at 

 the Mohawk mine, which seemed to be peculiar. It is tough, 

 but not so much as what I have called mohawk-whitneyite, 

 gray color and fine granular structure somewhat like algodo- 

 nite in appearance. 



B. B. reaction for antimony, no cobalt, no nickel. 



Spec. gr. 8-378 — 8-364 (with 1-747 grams) 



Cu = 80-72 

 As = 1912 

 Sb = 0-84 



63 = 1-281 



75 = 0255 



120 = 0-007 



100-68 

 Cu : (As,SbJ = 49 : 1 = 5 : 1 



