Wells and Penfield — JVew Occurrence of Sperrylite. 95 



Abt. VII. — On a New Occurrence of Sperrylite ; by H. L. 

 Wells and S. L. Penfield. 



Through the kindness of 'Professor Wilbur C. Knight of 

 the University of Wyoming at Laramie, we have received a 

 specimen of platiniferous copper ore from the Pambler Mine, 

 which is situated in the Medicine Bow Mountains about 50 

 miles southwest of Laramie. The specimen consisted chiefly 

 of covellite (indigo-copper) with a little pyrite. It occurred to 

 us that the platinum in this ore might exist in the form of 

 sperrylite, PtAs 2 , since this mineral, which we described* a 

 number of years ago, was found with sulphide ores in the Sud- 

 bury region in Canada, and since it has been shown by Walkerf 

 that the Canadian sperrylite occurs chiefly in copper minerals ; 

 hence we made an examination of the specimen. 



About an ounce of the ore was coarsely crushed, decomposed 

 with hot, concentrated nitric acid, and the residue was treated 

 alternately with boiling, strong caustic soda solution and nitric 

 acid until only a very small amount of dark-colored residue 

 remained. When this was freed from a little light-colored 

 material by decantation, about six very small glittering crys- 

 tals, resembling sperrylite, were observed with the naked eye. 

 After the material had been dried, the crystals were readily 

 picked out on a glass surface by the use of a lens and needle. 

 Under the microscope the crystals showed the wonderful bril- 

 liancy of sperrylite. The largest crystal measured 0*12 mm in 

 diameter and was rather highly modified. Although the com- 

 bination could not be determined with certainty, the forms of 

 the cube and pyritohedron were evidently present. A second 

 crystal was evidently a combination of octahedron and cube. 

 Four crystals having a total weight of about -00004 grams, 

 assuming that each had a diameter of 0'l mm which is a generous 

 average, were used for a chemical examination. Upon being 

 heated in the open tube they fused as sperrylite does and gave 

 a sublimate of arsenious oxide in white, octahedral crystals. 

 The residue in the tube was dissolved in aqua regia, and the 

 solution, upon evaporation with a little ammonium chloride, 

 gave yellow octahedral crystals of ammonium platinic chloride. 

 There is no doubt, therefore, that the mineral was sperrylite. 



We are not sure that the ore does not contain platinum in 

 some other form than sperrylite, but the fact that we did not 

 observe any metallic grains with this mineral makes it probable 

 that all the platinum in the ore exists as arsenide. 



* This Journal (3), xxxvii, 67 and 71 (1889). 

 f This Journal (4), i, 110 (1896). 



