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PROCEEDINGS OF THE NATIONAL MUSEUM 



considered as being entirely derived from the olivine. Hence, if we 

 know the magnesium and the silica content, the necessary quantity 

 of iron can be calculated and deducted from the total amount present. 

 Traces of calcium were also found, and as several tests for aluminum 

 gave negative results it seemed logical to consider the calcium as a 

 component of the olivine rather than as belonging to a soluble feldspar 

 molecule such as anorthite. 



Table 2 shows that the finely divided material contains 57.22 per- 

 cent olivine, while in the coarser samples 51.89 percent was found. 

 Since the relative proportion of these two fractions was not determined, 

 a weighted average of the olivine content in the meteorite cannot be 

 established, so the amount of olivine in the Chicora meteorite is 

 expressed by averaging the results obtained by recalculating the 

 analysis of these two groups. 



Table 4:.— Olivine in the Chicora meteorite {recalculated to 100 percent from the 

 results in table 2) 



The olivine composition expressed in weight percentages of the 

 various molecules is Mg2Si04, 60.67; FegSiOi, 37.63; Ca2Si04, 1.65. 

 If this olivine is compared with that found in terrestrial rocks it 

 will seem to be unusually high in iron. It is well above the average 

 iron content for olivines in pallasites, although the olivmes in stony 

 meteorites sometimes run as high in iron as this one. 



The indices of refraction determmed by the immersion method gave 

 values agreeing very well with the composition of this olivine: 



Bowen and Schairer, The system MgO-FeO-SiOj. Amer. Journ. Sci., vol. 29, p. 



The olivine in this meteorite has two different modes of occurrence: 



(a) There are fragments of a banded chondrulitic olivme structure 



(see pi. 59, A) but no complete chondrules. The banded or barred 



