Studies for Students 



THE CONSTITUENTS OF METEORITES. II 



Glass. — This is an abundant constituent of the stone meteor- 

 ites, few if any being entirely without it. It is variously dis- 

 tributed, occurring now as vein matter, now scattered through 

 the substance of chondri, now enclosed in the substance of a 

 single mineral, and now enclosing various minerals. 



In the Parnallee, Mezo-Madaras, Chassigny, Farmington and 

 a few other meteorites it has been described as forming a net- 

 work in which the other minerals are imbedded. Its ocurrence 

 in this manner is rare, however, it playing usually a merely acces- 

 sory part. It chiefly abounds as inclusions and intergrowths in 

 chrysolite, taking in this association a great variety of forms. 

 Other minerals too, frequently have inclusions of glass. It may 

 occur in fragments of considerable size or the particles may be 

 of a dustlike minuteness. 



Its abundance in chondri has already been mentioned. By all 

 these occurrences a rapid crystallization or cooling of the 

 meteorite substance is strongly indicated. Like the glass of 

 terrestrial lavas it seems to be the result of cooling so rapid as 

 to prevent differentiation and orderly crystallization of the 

 magma. The especial abundance of glass in meteoritic chrys- 

 olite, the least fusible and therefore the earliest cooling ingre- 

 dient further favors this conclusion. 



The prevailing color of the glass of meteorites is brown. 

 Much is however colorless and some occurs so dark as to be 

 opaque. Grayish and greenish tones occur but are rare. 



Chromite. — 'Nearly all stone meteorites give on analysis a 

 small percentage of chromium which is usually considered as 

 being present in the form of chromite, FeO,Cr203. The 

 mineral is not so abundant in the iron and iron-stone meteorites 



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