CHICORA METEORITE — PRESTON, HENDERSON, RANDOLPH 413 



ence of about 10 percent of CaSiOa is responsible for the lowering of 

 the indices. 



The finding of so much calcium metasilicate might suggest that 

 perhaps a member of the diopside-clinoh3^porsthene series was present 

 rather than hypersthene. However, the optical properties completely 

 disagree with diopside-hedenbergite. 



There are certain differences observed when one attempts to relate 

 the optical and chemical properties of this Chicora hypersthene. 

 It should be remembered that the optics were determined directly 

 on the grains present in the meteorite, while the composition expressed 

 for this mineral had to be obtained indirectly after deducting feldspar 

 and removing silica from the insoluble portion. Hence, less confidence 

 should be placed on the composition expressed for this hypersthene 

 than for any of the other minerals reported in this meteorite. 



The finding of two sets of indices and optical angles in this hyper- 

 sthene is difficult to explain properly. Theu* optical as well as their 

 physical properties are very closely similar, so that it is more than 

 likely there are not two distinctly and unrelated generations of 

 Iwpersthene present in this meteorite. It may be that at some time 

 this meteorite has been reheated to near the critical temperature for 

 the orthorhombic hypersthene and that a certain amount of inversion 

 has developed. Had the temperature reached much above 1,130° C, 

 the clinohypersthene should have formed and would have been 

 detected by the optical study. 



Plate 59, B, shows the boundary of a fragmental hypersthene 

 chondrule. There is a noticeable zone around the chondrule that has 

 a slightly different granular texture. This suggests that some adjust- 

 ment or reaction has taken place after the hypersthene chondrule was 

 added to this mineral aggregate. The fragmental nature of hyper- 

 sthene chondrules lends support to the suggestion that this mineral 

 aggregate has originated similar to terrestrial volcanic tuft's. 



METALLIC PORTION 



The largest inclusion of iron seen on a smooth surface, whose area 

 is about 6.5 square centimeters, is one with an over-all dimension of 

 about 1 millim.eter and its outline is more irregular than round. A 

 few smaller specks of iron can be detected. The percentage of metallic 



Table 7. — Metallic content of the Chicora meteorite 



