441 Koenig — MbhawMte, Stibio-domeyTcite, Domeykite, 



evident that at red beat the two elements form the compound 

 CirAs, leaving- much copper unaffected. The specific gravity 

 of this fused arsenide was found at 7*71, (3*8837 grams being 

 taken). The analysis gave 



Calculated for Cu 2 As. 



Cu 63-30 Cu 62-69 



As 37-00 As 37-31 



100-30 100-00 



The calculated specific gravity is = 7*754-, giving a minus 

 difference of 0*044 against the actual specific gravity. 



(b) The porous zone between a and the unaltered copper. 

 An ordinary lens showed that this mass consisted of groups of 

 minute crystals, exhibiting very brilliant faces. A power of 

 50 diameters differentiated the crystals easily. They appear to 

 be combinations similar to those of arsenopyrite. Believing 

 that I had found the method by which these crystals could be 

 prepared readily I destroyed them before making an attempt 

 at measurements, leaving only one group, and this one was lost 

 clumsily. There are still crystals on the copper cylinder show- 

 ing the forms and building up of the grape-like bunches but 

 I do not consider them worth the trouble connected with 

 micro-goniometric work. 253 milligrams of these groups, 

 which separate easily from the base, were taken for analysis 

 and only the copper was determined, as there could not be 

 anything but it and arsenic in the material. Found 



Cu = 71-39; theoretical for Cu 3 As = 71*6 Cu 



No doubt can exist as to the identity of these crystals with 

 domeykite. I have made several attempts since to get the 

 crystals but evidently did not hit the right temperature again. 

 I obtained domeykite as crystalline mass. In one experiment 

 I melted together 28*886 grams of the CirAs with 7*8 grams 

 of copper in a glass tube. Liquidity maintained for one hour. 

 After cooling the column was found of varying composition 

 from bottom up. The bottom portion showed a fracture sim- 

 ilar in color and structure to white iron, with a faint yellow, in 

 fact it looks exactly like the domeykite of Houghton Co. 

 Specific gravity = 8'05 ; percentage of copper = 75*4:, consider- 

 ably above the ratio Cn 3 As ; calculated specific gravity =8*085. 



Above this was found a laminated or scaly zone, resembling 

 some of the recently found domeykite from Sheldon location. 

 It gives copper = 71*14, very close to Cu 3 As. 



The top portion resembles in color and structure (very fine 

 grain) the CirAs. It gives copper = 64*8. 



