Plate 60 



1. Horse Creek, Colorado; an anomalous meteoric iron found in 1937, its original weight 

 570 grams; no analysis. It consists wholly of kamacite and schreibersite, the latter being 

 abundantly precipitated on the crystallographic planes of the phosphide. As explained on 

 page 64, those planes are not octahedral, although they have that appearance to the eye. 

 Owing to the brittleness of the phosphide the mass breaks easily with a highly perfect cleav- 

 age along the planes of the phosphide lamellae. In this specimen the section was made 

 on a plane that gives a pattern of triangles, resembling an octahedrite cut on an octahe- 

 dral plane. The structure in general is very regular, but in figures 1 and 4 deviations from 

 an octahedral pattern are apparent. Microscopic examination reveals in places as many 

 as six or seven planes of precipitation of the phosphide. Picral 70 seconds; X 60. U. S. 

 National Museum. 



2. Horse Creek. Occasionally there are coarser lamellae than appear in figure 1, of which 

 this is an example. Its substance extends into some of the finer lamellae. The very regular 

 fields are filled with minute phosphide particles, which are less plentiful near the lamellae. 

 Picral 40 seconds; X 150. 



3. Horse Creek. A large schreibersite inclusion with crystallographic planes. In its 

 immediate \'icinity the structure is modified, phosphide lamellae giving place to fine parti- 

 cles. Picral 120 seconds; X 30. 



4. Horse Creek. Hydroxide invading the structure. The oxide penetrates the mass 

 extensively in this manner, adding to its brittleness and ready cleav^age. Strong etching 

 here brings out granulation in the kamacite. Picral 120 seconds; X 30. 



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