T. L. Walker — Notes on Sperrylite. Ill 



edges formed by the intersection of the cubic faces with the 

 octahedral faces and with the new faces, form on the cubic 

 faces plane angles which gave the following measurements : 



155° 35' 156° 15' 



155° 55' 156° 20' 



156° 10' 156° 50' 



Average measurement, 156° 9'. 



Calculated for tt(10-5-2) 156° 49'. 



The calculated symbol for these new faces agrees very closely 

 with the di-dodecahedron 7r(10*5 - 2), which has not been previ- 

 ously determined for sperrylite; 7r(ll'5*2) occurs on pyrite and 

 is very close to the faces here described. There are still 

 other faces present on some of the crystals, but they are too 

 small to be determined on the present material. 



Small crystals are frequently observed, half-imbedded in 

 the cubic faces of the larger ones. These guest crystals 

 appear to possess the same orientation as the host, and 

 generally show combinations of (001) and (111). The hemi- 

 hedral faces may occur on the smaller individuals, but could 

 not be determined. In intergrowths of pyrite, the pyritohe- 

 dral faces are so disposed that the whole is regarded as inter- 

 penetration twins with the twinning axis normal to (110). This 

 is well seen in the so-called " iron cross." That the crystals of 

 sperrylite follow the same law of twinning is highly probable, 

 but we cannot regard it as proved from the present observa- 

 tions. The detection of pyritohedra or di-dodecahedra on the 

 guest crystals and the determination of their position with 

 regard to that of the corresponding faces on the larger crystal, 

 would settle the question beyond dispute. 



Sperrylite occurs in loose decomposition products of chalco- 

 pyrite, pyrrhotite and other iron-nickel sulphides. The con- 

 centrates obtained by "panning" consisted principally of 

 grains of chalcopyrite and pyrrhotite along with crystals of 

 magnetite, sperrylite, and cassiterite. The chalcopyrite grains 

 showed on closer examination that they frequently contain 

 crystals of sperrylite. The fragments of pyrrhotite were care- 

 fully examined, but in no case could crystals of sperrylite be 

 observed on them. The chalcopyrite is therefore the original 

 host of the sperrylite. In this connection it may be men- 

 tioned that in all the copper-nickel mines of the Sudbury dis- 

 trict, traces of the metals of the platinum group are found, 

 and also that nickel matte from mines low in copper contains 

 very little nickel, while mines richer in copper afford a matte 

 proportionally richer in platinum. In short, the platinum con- 

 tents of nickel matte in the Sudbury district is directly pro- 

 portional to the copper contents, viz : proportional to the 

 amount of copper pyrites in the original ore. This fact, taken 



