METEORITES — MASON AND MAYNES 



9 



the grains are turbid with tiny inclusions, which makes precise re- 

 fractive index measurements difficult. The hypersthene has a = 1.677, 

 7=1.688, indicating a content of 20 mole percent of the FeSi0 3 (Fs) 

 component, according to the determinative curve of Kuno (1954). 

 Dodd, Van Schmus, and Koffman (1967), by microprobe analysis, 

 reported a mean composition of Fs 20 .7 for the pyroxene with some 

 variability from grain to grain. 



In thin section under the microscope this meteorite is seen to be a 

 close-packed mass of chondrules, from 0.3 to 3 mm. in diameter, 

 with comparatively little interstitial material. A wide variety of 

 chondrules is present. Many consist of numerous euhedral crystals of 

 olivine and/or clinohypersthene in a turbid brown matrix that is 

 probably a devitrified glass. Barred olivine chondrules — the bars being 

 alternately olivine and turbid devitrified glass — are not uncommon. 

 Some chondrules consist of fibrous radiating clinohpyersthene, others 

 are made up of intergrown prismatic crystals of olivine and clino- 

 hypersthene. The opaque minerals are mostly interstitial to the chon- 

 drules or concentrated as rims around individual chondrules. 



The density of this meteorite, determined by the method described 

 for Allegan, was found to be 3.47. 



Table 3. — Chemical analysis and normative mineral composition of the Cynthiana 

 meteorite (analysis: Maynes; norm: Mason) 



Sum 



100.25% 



Chemical composition. — The chemical analysis and the normative 

 mineral composition calculated from it as recommended by Wahl 

 (1951) are given above. The observed mineral composition is in good 



