HANDBOOK OF THE METEORITE COLLECTIONS. 15 



and magnesia (MgO) in the meteorites. The presence of many of the 

 rarer elements tabulated as constituents of the terrestrial igneous 

 rocks has not as yet been fully determined in those of meteoric origin. 

 As has been noted, however, many of them have been found in 

 amounts too small to estimate. 



As already stated, the iron or metallic meteorites consist essentially 

 of alloys of iron, nickel, and cobalt, with Avhich are commonly asso- 

 ciated the phosphide schreibersite and the sulphide troilite. In mi- 

 nute quantities there may be other constituents, as copper, chromium, 

 and various silicate minerals. It is in these metallic forms also that 

 have been found the rarer elements — platinum, palladium, iridium, 

 ruthenium, and vanadium, and possibl}^ gold. Farrington's tabula- 

 tion of analyses seems to show that the nickel content varies with the 

 texture, the higher percentages of this constituent being found in those 

 of finest crystallization. The variation is, however, by no means con- 

 stant. In the table on the following page is given a selected series 

 of what are considered authentic analyses of the principal types of 

 iron, and also, for purposes of comparison, two examples each of 

 metal separated from the silicatet portions of pallasites and stony 

 meteorites. 



