258 /:'. Cohen — Meteoric Iron from Soudan. 



Such peculiarities of structure are unknown to me in any 

 other meteoric iron. It seems to me quite plausible that this 

 Mas originally a coarsely granular octahedrite, like Zacatecas, 

 which in consequence of its very flat form softened throughout 

 its mass, perhaps to the melting point, as it entered the 

 atmosphere. In the subsequent rapid cooling there was not 

 time enough for a normal crystallization — formation of octa- 

 hedral lamellae. Alloys rich in nickel could not unite so as to 

 form symmetrical taenit lamellae; but, during precipitate crys- 

 tallization, separated into the finest spangles which in their 

 habit arranged themselyes so as to be oriented parallel to the 

 octahedral planes, while the remainder uniformly solidified to 

 a compact plessite-like nickeliferous iron. 



This assumption of the softening or melting of the entire 

 mass of the meteorite, however unusual, is supported by a 

 large number of phenomena which, up to the present, have 

 never been observed in any other iron. Among these pecu- 

 liarities are : — the fluid arrangement of the troilite ; the 

 absence of larger nodules, despite the unusual richness in sul- 

 phide of iron ; the lack of an alteration zone, along with the 

 possession of a completely fused crust; the tapering and 

 tongue-shaped projections, extended in the same direction ; 

 the pointed, wedge-like shape ; the unusually varied and in 

 part bizarre relief of the anterior surface; the perforations, 

 which cannot be attributed to the melting out of accessory 

 ingredients ; and the increased richness in troilites toward the 

 part of the meteorite which was rearmost in the course of the 

 flight. 



I consider that these phenomena prove N'Goureyma to be a 

 member of the Zacatecas group, which was remelted during its 

 passage through the air, and may be considered as a sort of 

 appendage to this group. The unusual richness in sulphide of 

 iron, moreover, could have had an influence on the disturbed crys- 

 tallization, just as in Zacatecas, rich in troilite, the octahedral 

 structure is less complete than in most of the normal octahedrites. 



The analysis which I have made gave the following results : — 



Fe 



m 



Co 



Cu 



Cr 



89-28 



9-26 



. . .. 0-60 

 0-04 



o-ii 



Nickeliferous iron 



Schreibersite 



Troilite 



Daubreelite 



Lawrencite 



97-28 

 0-32 

 1-75 

 0-30 

 0-02 



s 



0-77 



0-05 



0-04 



o-oi 



0-09 



Chromite 



0-09 



P 



c . 



Decomposed silicious 

 grains. 



0-24 



CI 



Chromite _. 



Specific gravity is 7 





100-00 



Residue ._. 



0-24 



■672 



100-49 

 Greifswald, Germany. 



