Plate 71 



1. San Fraxcisco Mouxtains, Arizona; finest octahedritc. Xi-Co 7.99 percent. The 

 zone of alteration is remarkably distinct. Nital 3 percent .iS seconds; X l/i- 



2. San Francisco Mountains. Fusion crust (right). The etching is so light that 

 the kamacite shows no structure; field of plessite near left center. Xital 3 percent 15 

 seconds; X 60. 



3. San Francisco Mountains. Kamacite in zone of alteration, showing irregular 

 secondary granulation. Fusion crust at right. Picral 4 minutes; X 60. 



4. San Francisco Mountains. An area at the inner boundary of tlie zone of alteration. 

 The broad kamacite band has been completely altered. In the narrow one above it the 

 alteration is incomplete, a few Neumann lines remaining. The band at the top shows no 

 change. Picral 3 minutes; X 60. 



191 



