THE CONSTITUENTS OE METEORITES 40? 



Magura and 0.8 percent, of the Cosby's Creek iron. The mineral 

 is usually associated with iron sulphide. With this it may be 

 intimately intergrown or the one may enclose the other. Its 

 texture is compact rather than foliated. Smith found that the 

 meteoric graphite oxidized much more rapidly than terrestrial 

 graphite on treatment with nitric acid and chlorate of potash. 

 This feature distinguishes it from the amorphous carbon separated 

 from cast iron. The meteoritic graphite is also very pure. 

 Although occurring in nodules of the size described, which must 

 have segregated from the surrounding mass, the ash amounted, 

 in an analysis made by Smith, to only i per cent. By ether was 

 extracted a small quantity of a substance made up of sulphur and 

 a hydro-carbon, which constituted the only other impurity. 

 Emphasizing the differences between meteoritic and terrestrial 

 graphite Smith was inclined to believe that the graphite of 

 meteorites must have been formed by the action of bi-sulphide 

 of carbon upon incandescent iron rather than that it was analo- 

 gous in its origin to terrestrial graphite. Ansdell and Dewar, 

 however, concluded from elaborate comparisons of meteoric and 

 terrestrial graphite that they were similar in origin, and were 

 formed by the action of water, gases and other agents on 

 metal carbides. Whatever its mode of formation the occur- 

 rence of graphite in meteorites is of geological interest as 

 proving that graphite may be formed in nature without the 

 agency of life. 



Coheiiite. — This is a carbide of iron, nickel and cobalt. It 

 has been positively identified in only a few meteorites but is 

 doubtless of common occurrence. Its formula is (Fe, Ni, €0)3 

 C. The mineral is of metallic luster and tin-white color, though 

 readily tarnishing to bronze-yellow. Hardness, 5.5-6. Specific 

 gravity, 7.23-7.24. Strongly magnetic ; ver}^ brittle. Insoluble 

 in dilute hydrochloric acid and decomposed by concentrated 

 hydrochloric acid only with difficulty. Easily soluble in copper- 

 ammonium chloride. It occurs as isolated crystals on which 

 several forms of the isometric system have been noted ; also as 

 grains. Elongated crystals, reaching a length of 8™"" are 



