Plate 10 



1. Cincinnati, Ohio; nickel-poor ataxite; Ni-Co 6.11 percent, P 0.05 percent. Typical 

 structure. Rhabdites and schreibersite needles are rounded and diffused by heating. In 

 places the alteration is less complete, rhabdites being regular in shape with little diffusion. 

 Picral 40 seconds; X 150. American Museum of Natural History. 



The very low percentage of phosphorus shown in the analysis (Sjostrom, 1898) seems 

 inconsistent with the abundance of phosphide, not only as shown in the photograph but also 

 in needles and numerous inclusions of phosphide eutectic (pi. 59). 



2. Locust Grove, Georgia; nickel-poor ataxite; Ni-Co 6.21 percent. General structure, 

 showing effects of heating upon rhabdites and upon larger undetermined inclusions, which 

 probably are Fe-FesP eutectic. A unique structure in this iron is shown in plates 65 and 66. 

 Picral 30 seconds; X 60. 



3. Primitiva (La Primitiva), Chile; nickel-poor ataxite; Ni-Co 5.43 percent, P 0.18 per- 

 cent, C 0.03 percent. General structure, with a lamella of schreibersite. Though with so 

 low a Ni-Co content this iron might be assumed to be wholly in the alpha phase, nevertheless 

 it shows a transformation structure of gamma-alpha needles in kamacite similar to that 

 found in many octahedrites (e. g., Trenton, Canton, Thunda, pi. 35). Though exceptional 

 in irons so low in nickel, analogous structures were found in New Baltimore (Ni-Co 6.74). 

 plate 77, and San Francisco del Mezquital (Ni-Co 6.33 percent; pi. 78). 



4. Primitiva. The general structure at high magnification. The nature of the gamma- 

 alpha needles is clearer. Picral 20 seconds; X 600. 



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