Plate 31 



1. Limestone Creek, Alabama; nickel-rich ataxite; Ni-Co 30.47 percent. This extraor- 

 dinarily high-nickel iron is surpassed in nickel content only by Santa Catharina and 

 Octibbeha County. Its two-phase gamma-alpha structure is irregular. Despite its high 

 nickel content, it contains in places a profusion of kamacite needles (lamellae), sometimes 

 regular!)^ oriented. The photograph shows such needles, which appear larger than they 

 are because surrounded by areas of clear taenite. Picral 20 seconds; X 60. Field Mu- 

 seum of Natural History. 



2. Limestone Creek. An example of oriented needles. The taenite, strongly predom- 

 inating in the groundmass, does not form borders around the needles, as in lower nickel 

 ataxites, but forms a clear homogeneous field in which the needles and particles lie. The 

 black spots are oxidized kamacite. Picral 10 seconds; X 600. 



3. Limestone Creek. An example of the more irregular two-phase structure. Kama- 

 cite shows considerable oxidation. Picral 10 seconds ; X 600. 



4. Limestone Creek. One of the larger kamacite bodies, in an area of taenite, sur- 

 rounded by oxidized groundmass. Picral 10 seconds; X 600. 



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