S. L. Penfield — Pentlandite from Sudbury, Ont. 493 



Akt. LVIX. — On Pentlandite from Sudbury, Ontario, 

 Canada, with Remarks upon three supposed new species 

 from the same Region / by S. L. Penfield. 



Pentlandite. 



Up to the present time the occurrence of pentlandite at the 

 Sudbury nickel and copper mines has never, to the author's 

 knowledge, been definitely proved. Some years ago Mr. F. 

 L. Sperry, then chemist of the Canadian Copper Company, sent 

 a suite of Sudbury ores to the Sheffield Scientific School and 

 several of these were carefully analyzed by Mr. J. F. McKenzie, 

 a student at the time in the Sheffield Laboratory. His results 

 have been published only as a private contribution in the sixth 

 edition of Dana's Mineralogy. Analysis 17, page 74, is of a 

 nickeliferous pyrrhotite, with Fe = 56*39 and Ni = 4*66 per 

 cent. Analysis 3, page 65, is of a normal sulphide of iron and 

 nickel, with Fe = 25*81 and Ni = 39*85 per cent, the latter 

 including a trace of cobalt. The specimen from which the 

 material for the latter analysis was taken was a piece of mas- 

 sive ore, apparently very pure. The writer examined it care- 

 fully for indications of isometric crystallization or octahedral 

 cleavage, but none could be found ; it seemed to break every- 

 where with irregular fracture. The specimen was referred, 

 however, to the isometric pentlandite because it agreed .better 

 in its chemical composition with that species than with 

 pyrrhotite. 



Later, among the same lot of specimens sent by Mr. Sperry^ 

 a piece was found composed mostly of massive pyrrhotite but 

 showing in places a mineral lighter in color and which broke 

 with flat surfaces. On separating some of the latter it was 

 found to differ from pyrrhotite in being non-magnetic and giv- 

 ing a strong reaction for nickel before the blowpipe. More- 

 over on a number of pieces the angle between the flat surfaces 

 was measured twelve different times on the reflecting goni- 

 ometer within the limits 70° 23' and 70° 46', giving as a mean 

 70° 33', which agrees well with the angle of the isometric 

 octahedron 70° 32'. Three of the above angles were measured 

 in different zones on a single fragment. There is no doubt, 

 therefore, but that the mineral in question is isometric. The 

 flat surfaces are apparently not the result of an octahedral 

 cleavage but rather planes of parting, of secondary origin, 

 similar to the octahedral parting observed on some varieties of 

 magnetite.* The fracture of the mineral is irregular and the 



*A. Cathrein, Zeitschr. Kryst., xii, p. 47, 1886. 0. Miiggs, Jahrb. Min., i, p. 

 244, 1889. J. F. Kemp. This Journal, xl, p. 62, 1890. 



