Koenig — Weiv Species Melanochalciie and Keweenaioite, 411 



pinkish brown. On exposure tarnishes to a deeper brown 

 red ; but is far more constant towards the atmospheroids than 

 domeykite or mohawkite. I have now some specimens before 

 me which have been exposed to the laboratory gases for over 

 a year and still show the characteristic color, but slightly 

 deepened. Specific gravity at 20° C. = 7-681 (with 3-11:0 

 grams of the mineral). 



Chemical Characters. — B. B. melts easily to a globule. 

 Gives vapors of arsenic. On continued blowing in oxidizing 

 flame, a metallic globule is obtained. But if a borax bead be 

 placed along the globule from the first, while the O. F. is act- 

 ing, then a blue glass is obtained ; later a brown glass, and 

 ultimately a green glass, showing successively cobalt, nickel, 

 copper. The qualitative behavior is thus identical with 

 mohawkitd. Dissolves in concentrated Hl^Og and even in 

 HKO3 (Specific gravity 1-2). 



A first preliminary quantitative determination gave Cu = 

 38-5 ; (JSTi + Co) = i7-9S; quartz = 1-52; no iron— the dif- 

 ference must be arsenic. This was very different from 

 mohawkite. 



A second analysis of the same sample, carefully made with 

 O, 500 grams, gave 



0-0249 insoluble 



O-.sreo Mg^As^^ 



0-2449 Cu^S 



0-0945 Ni -h Co (by hydrogen) 



0-0047 Co (by hydrogen). 



From this follow the percentages. 



Quartz = 4-98 



As = 36-96 : lb = 0-493 



Cu — 39-12 : 63 = 0-621 



Ni = 17-96 ) . .^.. „ „^_ V 0-944 



Co = 0-94 \ ' ^^ ^ = ^^-' ^ 



Fe = trace 



99-96 



Thus the ratio obtains As : (Cu,Ni,Co) = 1,000 : 1,915 and 

 again Cu : (Ni + Co) = 2 ; 1 nearly. 



It was assumed by me that this ratio between the metals 

 would probably not be constant ; but instead to a certain limit 

 a replacement of each by the others, the same as was assumed 

 for the mohawkite and has been fully proven by numerous 

 analyses, I have made since. 



Keweenawite = (CujNijCo), As. 



