Plate 68 



1. San Francisco del Mezquital, Mexico; nickel-poor ataxite; Ni-Co 6.33 percent. 

 An area near the surface showing dark masses of invading hydroxide, which also has pene- 

 trated somewhat into the iron along grain boundaries. All dark particles are oxide, as no 

 metallic components would be visible without etching. Lnetched;X 60. American Museum 

 of Natural History. 



2. San Francisco del Mezquital. An area of which a portion appears in the upper 

 right part of figure 1. Etching darkens the grain boundaries between the oxide particles, 

 and also reveals a faint secondary granulation (due to reheating) within the larger grains. 

 Picral 40 seconds; X 60. 



3. Deep Springs, North Carolina; nickel-rich ataxite; Ni-Co 14.14 percent. The 

 paraeutectoid structure shown in plate 21 invaded by hydroxide which preferentially affects 

 the kamacite areas. Light picral; X 600. 



4. Holland's Store, Georgia; granular hexah'edrite; Ni-Co 6.35 percent. Intergranular 

 invasion of hydroxide (below) near the surface of the mass. (Compare plate 6.) Picral 

 75 seconds; X 30. 



188 



