Plate 42 



1. Pine River, Wisconsin; an undescribed iron that may be provisionalh- classitied as an 

 atypical coarsest octahedrite with accessor}- silicates. A field of plessite showing incomplete 

 transformation, bordered by taenite which is gray by reason of supersaturation. The acic- 

 ular structure, oriented on octahedral (gamma) planes, is composed of a gamma-alpha 

 aggregate. It is unchanged with picrate etching. The separation of the two phases is more 

 complete in the right portion; in the left portion, which is larger, more of the dense untrans- 

 formed aggregate was trapped in the interior. Light picral; X 60. 



2. Pine River. Part of the right portion of the field in figure 1. An imperfectly devel- 

 oped paraeutectoid structure has been attained, resembling that in a number of nickel-rich 

 ataxites. Near the taenite border the gamma phase has been absorbed, leav^ing clear kama- 

 cite. Light picral; X 300. 



3. Pine River. Part of the left portion of the field in figure I. The abundant dense 

 gamma-alpha aggregate is mostly unresolved at 1,000 diameters. Light picral; X 300. 



4. Barranca Blanca, Chile; listed as a brecciated (more properly granular) octahedrite; 

 Ni-Co 8.66 percent. An area of taenite with incompletely transformed core. Heavy Neu- 

 mann lines. Picral 60 seconds; X 60. American Museum of Natural History. 



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