COMPOSITION AND STRUCTURE OF METEORITES 



feldspar is oligoclase, a form characteristic of rocks of intermediate 

 acidity, as the diorites. The name maskelynite, it should be said, 

 was given by Tschermak ^ to an isotropic, colorless mineral abundant 

 in the Shergotty meteorite, and commonly considered a re-fused feld- 

 spar. With this most workers agree, regarding it a product of meta- 

 morphism.io (See pi. 3, fig. 1, also pi. 16, fig. 2.) The mineralogist 

 Groth, on the other hand, was inclined to believe it to be a species 

 allied to leucite. The feldspars are common constituents of mete- 

 orites of the basaltic types, such as that of Juvmas, in France, 

 where they occur in elongated polysynthetically twinned forms as in 

 terrestrial rocks. In the chondritic types ihey occur as scattered 

 granules occupying the interspaces of the olivines and enstatites, 

 and often quite lacking in crystal outlines or twinning bands, in which 

 case their satisfactory determination is a matter of difficulty. In 

 many meteorites of the chondritic type, and in most pallasites, 

 feldspars are wholly lacking. 



Analyses of meteoric feldspars 



' Borgstrom, Bull. Comm. Geol. Finlande. 

 » Lindstrom, Ofv. Kongl. Vet. Akad. Forhandl., 1869, p. 723. 

 5 Tschermak, Sitz. Akad. Wiss. Wien, vol. 65, 1872, p. 130. 

 * Shannon, Am. Museum Novitates, Nov. 30, 1925. 



Gases. — The fact that hydrogen was given ofi" when the Lenarto, 

 Italy, meteoric iron was heated in a vacuum, was first noted by 

 Thomas Graham in 1867. Prof. J. W. Mallet, in 1872, found that 

 the meteoric iron of Augusta County, Va., under similar circum- 

 stances yielded not merely hydrogen but also nitrogen, carbon mon- 

 oxide (CO), and carbon dioxide (CO2). Prof. A. A. Wright, in 1875 

 and 1876, showed that in the stony meteorites the gas was chiefly 

 in the form of the dioxide, or carbonic acid (CO2) as it is commonly 

 called, while in the irons the monoxide (CO) and hydrogen prevailed. 

 Doubts, if such there may have been, concerning these first announce- 

 ments would seemingly have been completely eliminated by the 

 later work of R. T. Chamberlin " from whose paper have been taken 

 bodily the tables following. 



» Sitz. Akad. Wiss. Wien, vol. 65, 1872, p. 127 



10 Merrill, Geo. P., On Metamorphism in Meteorites, Bull. Oeol. Soc. America, vol. 32, 1921, p. 407. 



n The Gases in Rocks. Publ. No 106, Carnegie Institution of Washington, 1908. 



