Plate 50 



1. Helt Township, Indiana; coarsest octahedrite; no analysis. Typical irregular inclu- 

 sion of schreibersite. The darkened border is due in some measure to the effect of strong 

 etching along the interface but is chiefly an optical effect sometimes seen around schrei- 

 bersite inclusions; the inclusion having been left in relief by polishing, reflects light away 

 from its borders. Upper left, a body of taenite. Below, very coarse plessite field of taenite 

 lamellae. Picral 3 minutes; X 60. 



2. Helt Township. Alternating bodies of taenite (darker) and schreibersite (lighter) 

 along a grain boundary. Partial alteration by heating during atmospheric flight has pro- 

 duced a band of incipient granulation along the line of the inclusions in which Neumann 

 lines are obliterated. Picral 2 minutes; X 60. 



3. Smith's Mountain, North Carolina; fine octahedrite, Ni-Co 8.52 percent. Part of 

 a large irregular inclusion of schreibersite. The inclusion is bounded in several places 

 by a straight line (parts of it visible at top and bottom of the photograph) which apparently 

 marks a crystallographic plane. The surface was chipped in polishing. Picral 80 seconds; 

 X 30. U. S. National Museum. 



4. Braunau, Bohemia; hexahedrite; Ni-Co 6.13 percent. Typical irregular schreiber- 

 site body, characteristic of many hexahedrites. Three sets of indistinct Neumann lines. 

 Picral; X 60. 



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