45 



Other specimens from a cutting on the railway one 

 hundred yards west of Ormsby Junction are similiar in 

 character to the rock just described. Microsocopic 

 examination, however, shows that while less biotite is 

 present, the rock contains a large amount of a yellow 

 sulphide of iron, apparently pyrrhotite. Quartz and 

 orthoclase are the most abundant constituents in this 

 rock, which also contains a few grains of muscovite and 

 zircon, the former mineral occurring in occasional large 

 individual skeleton crystals. The grains of the yellow 

 sulphide have an irregular outline, or are present in the 

 form of little strings running parallel to the foliation of the 

 rock. When examined by reflected light, nearly every 

 grain of this sulphide is seen to have intimately associated 

 with it a black mineral with a metallic lustre, which is 

 evidently magnetite. This latter mineral usually forms a 

 border around the yellow sulphide, wholly or partially 

 enclosing it. These metallic minerals occur not only in 

 larger grains, but also as a fine dust scattered throughout 

 the rock. 



At one place by the side of the road bed a band of this 

 gneiss has been opened up by a small pit, being mistaken 

 for an iron ore. This variety of the rock is black in colour 

 on a fresh fracture, and when examined under the 

 microscope is seen to be composed chiefly of quartz, 

 hornblende and magnetite. The hornblende is arranged 

 in rudely parallel lines, giving the rock a distinct foliation. 

 It is deep green in colour, and distinctly pleochroic in 

 greenish and yellow tints. The magnetite has a black 

 metallic lustre, and frequently possesses a good crystalline 

 form. An immense number of very minute garnet 

 crystals occur through the rock, resembling those in the 

 rusty gneiss above described, but very much more 

 abundant. Although so small, they are rather uniformly 

 distributed, occurring not only in the hornblende and 

 quartz, but also in the magnetite. They are isotropic and 

 possess a good crystalline form. 



This band of gneiss suggests in its appearance in the 

 field certain belts of the magnetite-griinerite schist in the 

 iron ranges on the south side of Lake Superior. The 

 microscopic examination of the rocks, however, shows them 

 to be quite different from the schist in question, biotite 

 being the only iron-magnesia constituent present, except in 

 the case of the narrow band above referred to as having 



