Meteorite Collection — Handbook and Catalogue. 17 



These are usually present in combination, but hydrogen and 

 nitrogen occur as occluded gases and carbon in the elementary form 

 of graphite or diamond. 



The following compounds occur, which in chemical composition 

 and physical properties seem to be wholly similar to terrestrial miner- 

 als of the same name: 



The silicates, chrysolite (Mg, Fe) 2 Si 4 , enstatite, Mg Si O s , 

 bronzite, (Mg, Fe)Si O s , diopside including diallage, Ca Mg (Si O s ) 8 

 + Ca (Mg, Fe) (Si 0,)„ augite, Ca (Mg, Fe) (Si 3 ) 2 + (Mg, Fe) 

 (Al, Fe) 2 Si 6 , labradorite, (Na Al Si 3 O s + Ca Al 2 Si 2 O s ) and 

 anorthite, Ca Al 2 Si 2 O s ; the oxides, magnetite, Fe O, Fe 2 3 and 

 chromite, Fe O, Cr 2 O s ; the sulphides, pyrite, Fe S 2 , and pyrrhotite, 

 Fe, S 8 , and the carbonate, breunnerite Mg Co 3 with Fe O. 



Quartz, (Si 2 ), though so widely distributed upon the earth, is 

 conspicuous by its absence from meteorites. Small crystals have, 

 however, recently been observed in the crust of some of the Toluca 

 irons,* and free silica occurs in several meteorites in the form of asman- 

 ite, a compound believed to be identical with tridymite. Zircon, (Zr Si 

 4 ) has also been found in one of the Toluca masses, and the presence 

 of orthoclase, garnet and apatite in several meteorites is probable, 

 though not proved. Several soluble salts, such as chloride of sodium, 

 and sulphates of sodium, calcium and magnesium, have been found 

 in meteorites, and the carbonaceous meteorites contain bituminous 

 substances which closely resemble terrestrial bitumens. As occluded 

 gases occur marsh gas and carbon monoxide and dioxide. 



The soluble salts and breunnerite are regarded by Cohen as of 

 secondary origin, i. e., formed after the entrance of the meteorite in- 

 to the earth's atmosphere, and the same may be true of the gases and 

 bituminous substances. Various other compounds found in mete- 

 orites have from time to time been described as distinct species but 

 their identity with terrestrial minerals has later been established. 



The following compounds found in meteorites are believed to 

 have no representatives among terrestrial minerals: 



Various alloys of nickel and iron, including taenite, Fe 6 Ni, 

 kamacite, Fe 14 Ni, plessite, Fe 28 Ni 6 and edmonsonite; chalypitc, a 

 compound of iron and carbon ; cliftonite, a cubic form of graphitic 

 carbon; cohenite, (Fe, Ni, Co) 3 C; schreibersite, (Fe, Ni) 3 P; troilite, 

 Fe S ; oldhamite, Ca S ; osbornite, supposed to be a sulphide or oxysul- 

 phide of calcium and probably titanium; daubr^elite, Fe S, Cr 2 S 3 , 

 and lawrencite, Fe Cl 2 . 



The chemical character of these compounds indicates that the 

 conditions under which they were formed differed from those which 



♦Groth's Zeitscbr fur Kryst. und Min., Bd. 24. p. 485. 



