Plate 40 



1. RoEBOURNE, Australia; medium octahedrite; Xi-Co 8.92 percent. A light plessite 

 field, consisting of clear kamacite with a sparse distribution of taenite particles, between 

 granulated kamacite bands. The grain boundaries of the bands do not penetrate the field, 

 which has its own system of grains. Several taenite lamellae on lower side of field, but no 

 taenite border on upper side. Picral 60 seconds; X 60. 



2. San Francisco Mountains, Arizona; finest octahedrite; Xi-Co 7.99 percent. The 

 nickel-cobalt content is very low for a finest octahedrite. A very light plessite field con- 

 sisting of clear kamacite with droplike segregations of taenite along grain boundaries. 

 Nital 10 seconds; X 60. 



3. San Francisco Mountains. .A light plessite field, consisting of clear granulated kama- 

 cite with minute needles and particles of taenite di\ersely oriented. Some grains show 

 Neumann lines. Picral; X 60. 



4. San Francisco Mountains. Part of an area similar to figure 3 at high magnification, 

 showing taenite needles (sections of flakes) and irregular particles. This area is in the zone 

 of alteration; Neumann lines are obliterated and there is a faint pattern of secondary 

 granulation. The outlines of the original larger grains are marked b\- larger taenite bodies. 

 The analysis of this iron shows no phosphorus. Picral 3 minutes; X 600. 



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