59 



and patches enclosed by massive pyrrhotite, so that it is not hard to 

 separate considerable masses of chalcopyrite that will assay over 30 per 

 cent, of copper, or pyrrhotite that will only show traces of that metal. 

 In practice, however, careful examination and trial have proved that the 

 two minerals are too intimately associated to make sorting by hand at 

 all practicable, and the pyrrhotite is very often so feebly magnetic as to 

 preclude the possibility of separation by magnetism. Although the 

 chalcopyrite seldom occurs free from the pyrrhotite, large and massive 

 deposits of the latter occur comparatively free from copper. In this 

 connection Dr. Peters mentions a slope which, having furnished about 

 2,000 tons of pyrrhotite, gave place, just before the end boundaries 

 were reached, to a deposit which afforded nearly 20 tons of almost pure 

 chalcopyrite. In some instances these ore bodies show a brecciated 

 character, large angular or partially rounded boulders or "horses" of 

 almost barren rock being mingled with the ore, which seem to evidence 

 the disruptive force of the intrusive mass, while in others, as at the 

 Worthington mine, the diabase in which the ore occurs has developed a 

 concretionary structure while cooling, and large irregularly rounded concre- 

 tions, which, on weathering, peel off in concentric layers, are cemented 

 together, so to speak, by a very pure chalcopyrite and highly nickelifer- 

 ous pyrrhotite. The concretions themselves usually contain more or 

 less pyritous matter disseminated through them, but are usually cast 

 aside as too barren for the roast heap. The pyrrhotite varies in colour 

 from steel-grey to bronze yellow, and the chalcopyrite is the usual brass 

 or deep yellow colour. Both tarnish readily, and very beautiful 

 iridescent specimens can be easily obtained from the ore heap or 

 scattered around the works. These sulphides, therefore, may be said 

 to occur in three distinct ways — ■ 



ist. As contact deposits of pyrrhotite and chalcopyrite situated 

 between the clastic rocks, such as felsites, quartzites, etc., and irruptive 

 diabase or gabbro, or between these latter and granite or micropegma- 

 tite. Good examples of the former are furnished by the Evans, Stobie 

 and Copper Cliff, while the Murray mine may be cited as illustrating 

 the latter. 



2nd. As impregnations of these mmerals through the diabase or 

 gabbro, which are sometimes so rich and considerable as to form 



