Plate 59 



1. Rio LoA, Chile; hexahedrite; Ni-Co 5.71 percent. A needle and a large irregular 

 inclusion of schreibersite, showing remnant of phosphide-iron eutectic. In the needle the 

 phosphide-iron solution contracted to a central position; in the larger body it withdrew to 

 one side. Picral 150 seconds; X 60. 



2. Rio Lo.\. The same area as figure 1, with additional 5 minutes neutral sodium picrate. 

 The extensions of the phosphide-iron solution along grain boundaries were entrapped there 

 on cooling and remain isolated. The iron immediately surrounding the inclusions, as usual 

 in such cases, is phosphide-poor, shown by the absence of rhabdites and phosphide particles. 



3. Chesterville, South Carolina; nickel-poor ataxite; Ni-Co 6.25 percent, P0.34 percent. 

 Inclusion of schreibersite changed b\' heating to an iron-phosphide eutectic. The entire 

 iron underwent substantially the same change by heating as appears in the zone of alteration 

 in Rio Loa, which has a similar composition. The inclusion is almost uniformly eutectic 

 in composition, only a few droplets of kamacite ha\'ing been rejected during cooling. The 

 fluid eutectic invaded grain boundaries. Picral 40 seconds; X 150. U. S. National Museum. 



4. Cincinnati, Ohio; nickel-poor ataxite; Ni-Co 6.11 percent. An area of iron-phosphide 

 eutectic, similar in origin to the preceding. The eutectic structure is of unusual fineness 

 and regularity, and a considerable proportion of excess iron was rejected in cooling along the 

 interface and in droplike forms. The refinement of the structure indicates comparatively 

 slow cooling. Picral 60 seconds; X 60. American Museum of Natural History. 



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