COMPOSITION AND STRUCTURE OF METEORITES 



By George P. Merrill 

 Head Curator of Geologxj, United States National Museum 



ELEMENTAL COMPOSITION OF METEORITES 



A meteorite is a body of more than immediate miQeralogical or 

 petrographical interest. It furnishes tangible evidence of the nature 

 of materials existing in remote regions of our solar system and per- 

 haps beyond, and affords, aside from the spectroscope, the only clue 

 to the matter of which celestial bodies are composed and the condi- 

 tions, under which they originated, a fact recognized by Humboldt 

 many years ago. It is, therefore, of interest to compare the materials 

 that are now coming from space, or have come within historic times, 

 with those forming the rocks of the earth's crust. 



The most abundant of the meteoric elements are, named in alpha 

 betical order: Aluminum, calcium, carbon, iron, magnesium, nickel, 

 oxygen, phosphorus, silicon, and sulphur. In smaller quantities are 

 found chlorine, chromium, cobalt, copper, hydrogen, iridium, lithium, 

 manganese, nitrogen, palladium, platinum, potassium, ruthenium, 

 sodium, titanium, and vanadium, probably also argon and helium. 

 The presence of antimony, arsenic, gold, lead, strontium, tin, and 

 zinc have from time to time been reported, but recent investigation 

 throws doubt upon the correctness of the determinations.^ Tests 

 for fluorine have thus far yielded only negative results. 



MINERAL COMPOSITION OF METEORITES 



Though the elemental matter of meteorites may be the same as in 

 terrestrial rocks, the proportional amounts and forms of combina- 

 tion are at times radically different and of a nature to indicate that 

 they came about under conditions quite unlike those existing on the 

 earth to-day, and particularly so with reference to the presence of 

 free oxygen and moisture. It is for this reason in part that the study 

 of meteorites is so fascinating. 



The following list comprises the meteoric minerals which are also 

 constituents of terrestrial rocks: Olivine; the orthorhombic pyroxenes 

 enstatite, hronzite, or hypersthene; the monoclinic pyroxenes diopside 



> MerrUl, Geo. P., On the Minor Constituents of Meteorites. Amer. Journal of Science, vol. 35, 1913. 



p. 509. 



1 



