Plate 11 



1. Mejillones, Chile; nickel-poor ataxite; Ni-Co 6.26 percent, P 0.32 percent. This 

 iron is an aggregate of macrograins, averaging about a millimeter in size, with diversel}' 

 oriented sheen giving with ordinary etching an appearance of glistening flakes. The out- 

 lines of the large gamma grains have been preserved by impurities along the boundaries. 

 The iron is filled with minute phosphide particles whose peculiar shapes indicate heat altera- 

 tion. Picral 95 seconds; X 45. 



2. Mejillones. In the vicinity of the schreibersite inclusion the large grains give place 

 to finer and finer granulation, a condition found about such inclusions in other irons. In 

 artificial irons phosphorus inhibits grain growth. Picral 95 seconds; X 45. 



3. SoPER, Oklahoma; nickel-poor ataxite; Ni-Co 6.91 percent, P 2.23 percent. This un- 

 usual iron, with an extraordinary proportion of phosphorus, has a structure of large grains 

 with copious precipitation of schreibersite along the boundaries. Some minute particles of 

 phosphide are found within the grains; otherwise the kamacite is clear and structureless. 

 The phosphide obviously segregated in the gamma phase, contemporaneously with, or after, 

 the formation of the grains. The structure is the same with picral etching, except that the 

 phosphide areas are clear. Light picral and neutral sodium picrate; X 60. 



4. SoPER, nickel-poor ataxite. An area similar to the preceding. The phosphide bodies 

 are shown to have a mottled structure similar to those in Helt Township (plate 55), proba- 

 bly indicating an iron-phosphide eutectic. Light picral and neutral sodium picrate; X 150. 



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