2 BULLETIN 94, UNITED STATES NATIONAL MUSEUM. 



sible, as a rule, to separate them into three somewhat ill-defined 

 groups, as follows: 



Aerolites or Stony "I Consisting essentially of silicate minerals with minor 

 Meteorites. j amounts of the metallic alloys and sulphides. 



„.^ ,., cii. • „1 Consisting of an extremely variable network or sponge 



Siderolites or Stony-iron ^^ ^^^^^^ ^^^ interstices of which are occupied by 

 Meteorites. J ^^^ ^.^.^^^^ mineral. 



Siderites or Iron 1 Consisting essentially of an alloy of nickel-iron with 

 Meteorites. J iron phosphides and sulphides. 



Examples of these are shown in the introductory series in the case. 



Many attempts have been made at a more detailed classification 

 than that given above, the one most generally accepted being that 

 proposed by Dr. A. Brezina, formerly in charge of the meteorite 

 collections of the Austrian Museum, in Vienna. It is altogether too 

 technical for the general reader, and indeed the distinctions are often 

 founded on matters of such minor importance that fragments from 

 different portions of the same mass have been classed under quite 

 different heads. It is, however, the form followed here, though with- 

 out too great emphasis on what are believed to be matters of minor 

 import. It may be well to state in advance that the term chondrule 

 (Latin Chondrum and Chondri) refers to the peculiar spherical and 

 oval shapes often assumed by the silicate constituents, the formation 

 of which affords one of the most interesting puzzles in connection 

 with the origin of meteorites, and further, that all known meteorites 

 are of an igneous nature. 



CLASSIFICATION. 

 I. Meteoric Stones : Aerolites. 



A. Meteorites rich in calcium and aluminum-bearing minerals, 

 poor in nickel-iron and without chondrules. 



1. Angrite (A) : Consisting essentially of a calcium rich augite 

 with a little olivine and iron sulphide ; structure crystalline granular. 



2. Eukrite (Eu) : Consisting essentially of augite and anorthite 

 with a little iron sulphide; structure basaltic. 



3. Shergottite (Sh) : Consisting essentially of augite and maskely- 

 nite with a little magnesia ; structure crystalline granular. 



4. Howardite (Ho and Hob) : Consisting essentially of augite. 

 anorthite, bronzite, and olivine ; structure in part tuff-like and in part 

 crystalline. 



B. Meteorites rich in magnesian minerals, poor in nickel-iron, and 

 for the most part without chondrules. 



1. Bustite (Bu) : Consisting essentially of diopside and bronzite 

 with sometimes plagioclase, nickel-iron, osbornite, and oldhamite; 

 structure crystalline. 



