A Igoclonite and some artificial copper-arsenides. 447 



his analysis the ratio Cu 4 As (including ~Ni + Co) and says that 

 with this formula Mohawkite will probably be accepted by 

 science. If this ratio does exist then it is not Mohawkite ; for 

 this name was given by me to Cu 3 As (including JSTi + Co). But 

 the following sentence regarding the material induces me to 

 believe that it was a mixture of Mohawkite and Whitneyite. 

 The report says : " The sample was pulverized and concentrated 

 by washing until under a powerful glass no other minerals were 

 present. Thus purified the mineral was analyzed with the 

 following result : Cu = 68-6 ; As = 22-67 ; Ni = 6-55 ; Co = 

 1*2 ; Fe = 0*23 ; S = - 53. The sulphur and iron are impuri- 

 ties [why ? if the powerful glass showed no other minerals 

 present 1 Koenig] and it is also reasonably probable that the 

 nickel and cobalt are mechanically mixed in the sample, 

 although it is possible that some of the copper has been replaced 

 by nickel and cobalt." How can Dr. Ledoux calculate a 

 formula at all if he holds such views as here expressed % He 

 gives the. specific gravity at 7'8, but as I have shown above, a 

 composition such as he finds must have a higher specific 

 gravity even than I find for the Mohawkite proper, namely 

 8*140, leaving out both iron and sulphur. The atomic quo- 

 tients of Dr. Ledoux's percentages are : 



Cu 1-089 As 0-302 



Ni__ o-lli 



Co 0-020 ■ 



1-220 



giving the ratio of 4:1, but if nickel and cobalt are thrown 

 out the ratio is nearer 3 : 1 than 4:1. 



Under the existing conditions 1 permit myself to doubt the 

 existence of a molecule (Cu, Ni, Co) 4 As and merely present 

 the facts to the mineralogical public. 



4. Algodonite. 



This species has not yet been observed at the Mohawk mine, 

 though some of the Mohawk-Whitneyite resembles it very 

 much. I was induced to bring it within the present investiga- 

 tion merely by the specific gravity, which is given by Dr. F. A. 

 Genth as the only authority at 7'62. To Dr. Lucius Hubbard 

 I am indebted for the material. This gentleman possesses a 

 handsome specimen from the find at the Pewabic mine, many 

 years ago. The specimen looks like the segment of a nodular 

 piece. It showed the chocolate-brown dull tarnish. But the 

 fresh fracture is beautiful. It has a color and texture exactly 



