Plate 65 



1. Locust Grove, Georgia; nickel-poor ataxite; Xi-Co 6.21 percent, P 0.18 percent, 

 C 0.02 percent. Interface of a large inclusion showing (above) a coarse dendritic structure 

 with a zone (below) of acicular structure. The former apparently consists of dendrites of 

 an Fe-FeaC aggregate (gray), surrounded by the Fe-P-C eutectic (clear white) known in 

 artificial irons as steadite (Fe, FesP, FesC), all in a mottled nearly black matrix having the 

 appearance of an iron-graphite eutectic in artificial irons (see Chapter \TI). The acicular 

 portion is a form of Fe-FeaC Widmanstatten structure. With light etching no structure 

 is shown in the adjacent kamacite below. Picral 30 seconds; X 45. 



2. Locust Grove. Part of the dendritic area shown in figure 1. It resembles a struc- 

 ture in a high-phosphorus cast iron. The rounded or elongated gray bodies are the Fe-FesC 

 aggregate referred to above. The perfectK" clear matrix surrounding them is steadite. 

 The dark mottled areas are apparently an iron-graphite eutectic. Picral 30 seconds; X 45. 



3. Locust Grove. The identical area shown in figure 2 with additional etching 3 

 minutes with neutral sodium picrate. The clear areas shown in figure 2 are now black, 

 indicating that they are the phosphide eutectic. The gray dendrites are unaffected, indi- 

 cating that they are an Fe-FcaC aggregate. The dark mottled areas are unchanged (black 

 with white flecks), indicating that the}- are a phosphorus-free aggregate of nickel-iron and 

 eraphite. 



4. Locust Grove. A portion of the area shown in figures 2 and 3, unetched; X 300. The 

 component that is \-isible unetched is that of the mottled black areas in figure 2, showing 

 a gray color suggesting the appearance of graphite in artificial iron. The large clear area 

 corresponds with the other components in figure 2 — the gray dendrites and the clear phos- 

 phide eutectic surrounding them; being wholly metallic these show no structure without 

 etching. 



185 



