THE CONSTITUENTS OF METEORITES 395 



ESSENTIAL ACCESSORY 



Nickel-iron Included gases 



Chrysolite Iron sulphide 



Orthorhombic pyroxene Schreibersite 



Monoclinic pyroxene Graphite 



Plagioclase Cohenite 



Maskelynite Glass 



Chromite 



Amorphous carbon 



Diamond 



Daitbreelite 



Tridymite 



Lawrencite 



Magnetite 



Oldhamite 



Hydro carbons 



A brief account will be given of each of these. 



Nickel-iroji. — This is the most widely distributed constituent 

 of meteorities and in quantity it exceeds all the others combined. 

 It makes up practically the entire mass of all the iron meteorites, 

 the larger part of the mass of the iron-stone meteorites and is 

 found in nearly all, though not all, the stone meteorites. It is 

 an alloy of iron and nickel in which the percentage of nickel 

 varies from about 6 per cent, to about 20 per cent. Some iron 

 masses claimed to be meteorites contain a higher percentage and 

 some authorities regard the nickel-iron of most stone meteorites 

 as generall}' containing from 20 to 40 per cent, of nickel, but 

 this is somewhat uncertain. From 0.5 to 2 per cent, of cobalt 

 always accompanies the nickel, as well as .006 to .02 per cent, 

 of copper. Traces of manganese and tin are also often found. 

 The terrestrial nickel-iron of the Greenland basalts differs from 

 that of meteorites in having a lower percentage of nickel (0.25 

 to 4 per cent.) and in containing a considerable amount (3 per 

 cent.) of carbon. The terrestrial nickel-irons known as awaruite 

 and josephinite contain higher percentages of nickel than the 

 meteoritic, the percentages being 67.7 per cent, and 30.5 per 

 cent, respectively. In color, meteoritic nickel-iron varies from 

 iron or steel-gray to silver-white, according to the percentage of 



