Plate 12 



1. Butler, Missouri; finest octahedrite; Ni-Co 10.28 percent. A very regular Widman- 

 statten structure, the taenite approaching the kainacite in area, and all plessite fine to 

 dense. The field at left shows kamacite needles (lamellae) octahedrally oriented. Picral 

 35 seconds; X 30. 



2. Butler. With light etching the plessite shows a structure of white alpha (kamacite) 

 particles in a black gamma-alpha mixture of extreme fineness. Picral 10 seconds; X 150. 



3. Butler. One of the occasional plessite fields that are filled with a prcfusion of 

 kamacite particles and needles octahedrally oriented. Picral 35 seconds; X 30. 



4. Butler. Part of the area shown in figure 3 at higher magnification. The kamacite 

 bodies are surrounded by clear taenite. The ground mass of the iron in part consists 

 largely of kamacite particles; in places it is a black unresolved gamma-alpha aggregate. 

 The structure resembles that of some nickel-rich ataxites. Picral 10 seconds; X 150. 



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