NO. 5 IlEXAHEDRITES — HENDERSON 33 



were obtained in some unpublished work on other meteorites at the 

 U. S. National Museum. 



The Lake Murray, Okla., iron (pi. 1), shows an octahedral pattern 

 with kamacite bands more than 1 cm. wide, but where the large 

 skeletal growths of schreibersite form, the octahedral structure in the 

 matrix is disrupted. The dark square areas are patches applied to 

 protect troilite from being attacked by the etchant. Modern etching 

 techniques have found this precaution unnecessary. 



The Bellsbank, South Africa, iron (pi. 2), is a hexahedrite with 

 large schreibersite inclusions. The thin lamellae at the left intersect 

 each other at a variety of angles and are filled with an alteration 

 product. The Neumann lines in the kamacite extend to the breaks, 

 then continue on the other side of the lamellae without a change of 

 direction. Along these lamellae the kamacite is clear, compared with 

 the kamacite more remote from them. 



The kamacite surrounding the schreibersite in the Bellsbank iron 

 also is slightly lighter in color than the kamacite remote from the 

 phosphide bodies. If iron is rejected from schreibersite as the 

 temperature falls, of if nickel from the surrounding kamacite enters 

 the phosphide in preference to iron, this may explain the clear 

 kamacite. 



The Santa Luzia, Brazil, meteorite (pi. 3), like the Lake Murray, 

 Okla., iron, is a coarse octahedrite with wide kamacite bands, some 

 about 1 cm. wide. However, when schreibersite forms a skeletal 

 habit, the enclosing kamacite becomes equidimensional, and such 

 kamacite bodies disrupt the octahedral pattern. Since the slice 

 illustrated is 0.5 cm. thick, and this schreibersite body is about 

 equally large on both sides of the slice, it probably continued into 

 adjoining slices, thus some conception of its size can be made. 



The dark triangular area in the central phosphide body is troilite. 

 In places, the troilite makes a direct contact with the schreibersite ; 

 elsewhere, it is in direct contact with the kamacite. Schreibersite more 

 commonly occurs surrounding the troilite. 



The Central Missouri iron (pi. 4) was found between 1850 and 

 1860, but the chemical analysis given by Preston (1900) does not 

 appear to be reliable. After Perry (1944) reexamined this iron, he 

 considered it to be a granular hexahedrite and placed it in the 

 transitional zone between coarse octahedrites and hexahedrites. The 

 Central Missouri iron resembles very closely the Ainsworth, Nebr., 

 meteorite. Both contain large skeletal schreibersites and some 

 alteration products in the fractures separating the coarse kamacite 



