EXPLANATION OF PLATE 13 



Fig. 1. Nickel ore. Creighton Mine, Sudbury. 



Pentlandite, pn; pyrrhotite, p; magnetite, m; silicates, s. 



Fig. 2. Nickel ore. Creighton Mine, Sudbury. X 17. 



"Veins'' of pentlandite in pyrrhotite. (Fig. 35, Tolman and Rogers.) 



Fig. 3. Cast manganese steel. X 78. 



"Veins'' of ferrite in groundmass of other iron substances. (Figure 4, Young, 

 Pease and Strand, Trans. A. I. M. E., vol. L.) 



[250] 



