Plate 53 



1. Walker County, Alabama; hexahedrite; Ni-Co 5.94 percent, P0.28 percent. Rhab- 

 dites surrounded by oxide. One rhabdite is free from oxide. Tiiat the dark aureoles are 

 oxide, and not diffused phosphide (as in some cases), is indicated by the sharp unaltered 

 angles of the crystals. It is definiteh' proved by the fact that the\' are \isible on an unetched 

 surface. Picral 40 seconds; X 600. 



2. Walker County. An area showing rhabdites and phosphide particles surrounded by 

 oxide, and also long tine needles (like those in pi. 52, fig. 3) bordered b\- oxide. Unetched; 

 X 60. Field Museum of Natural Histor}'. 



3. Rio LoA, Chile; hexahedrite, Ni-Co 5.70 percent. General structure of the iron, 

 normal rhabdites and Neumann lines. This iron etches slowly. Picral 150 seconds; X 60. 



4. Rio LoA. An area in the zone of alteration near edge of slice, where the structure has 

 been changed by superficial heating during atmospheric flight. Neumann lines are obliter- 

 ated and rhabdites ha\"e been changed by fusion into shapeless particles. Picral 150 sec- 

 onds; X 60. 



173 



507394—44 IG 



