EXPLANATION OF PLATE 11 



Fig. 1. Massive ore, Friday Mine. X 25. 



Note the vein-like mass of chalcopyrite in the pyrrhotite. This vein stops 

 abruptly against the silicate, showing that the two sulphides act as a unit in their 

 textural relations with the silicates. 



Fig. 2. Polished surface of norite. X 233. 



Two simple grains of pyrrhotite inclosed within a single, fresh, unfraetured 

 silicate. Note that each of the pyrrhotite grains contains a minute mass of 

 pentlandite. 



Fig. 3. Polished surface of peridotite. X 108. 



A vein-like mass of pyrrhotite connecting two grains of that mineral. Note the 

 tiny ' ' bar ' ' of pentlandite lying across the vein-like mass near its middle por- 

 tion, the pentlandite terminating abruptly against the silicate walls. 



Fig. 4. Polished surface of peridotite. X 233. 



Vein and grain of pyrrhotite inclosed in silicates. The vein-like masses shown 

 in figures 3 and 4 are wholly exceptional, the two figured here being the only 

 ones found in the detailed examination of eight specimens. 



Fig. 5. Polished surface of olivine gabbro. X 125. 



Shows a compound grain of pyrrhotite, white, and magnetite, gray. 



Fig. 6. Polished surface of olivine gabbro. X 108. 



Pentlandite at edge of a pyrrhotite grain. 



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