306 0. O. Farrington — Analysis of "Iron Shale." 



FeO 



_ 74-63 



A1.0, .... 

 S0 3 



s ._ 



V.::-:- 



C ... 



Cl 



0=C1= 



o=p= 



0*05 



FeO _ 



3*91 



o-oo 



NiO 



9-79 



tr. 



CoO 



CuO 



CaO 



MgO 



HO 



0*49 



0-00 



1-27 



o-oo 



8*02 



, o-oo 

 o-io 



0-15 

 0-08 



99*93 



SiO 



1-09 



o-oi 



co, 2 



0-35 



0-15 



99-77. 

 The results of this analysis confirm the statements of 

 Koenig and Barringer that nickel and cobalt are to be found 

 in the shale in the same proportion as in the meteoric iron, 

 and leave little doubt that the " shale " is derived by oxidation 

 from the meteoric iron. It is obvious that the analysis may 

 be interpreted in several ways, since much uncertainty exists 

 as to what changes iron undergoes in the process of ci rusting." 

 By some it is thought that a ferrous carbonate is first formed 

 which later alters to ferric hydroxide. Others doubt the influ- 

 ence of carbonic acid and believe that the oxygen and water 

 of the air produce ferrous oxide and hydrogen peroxide. By 

 the first process it would be expected that limonite alone 

 would be produced, while the second might form some magne- 

 tite. Examination under the microscope of the finely pow- 

 dered shale showed differences of color and texture not observ- 

 able to the naked eye. In the small grains appeared alter- 

 nations of black and yellow colorings and compact and earthy 

 textures which suggested associated magnetite and limonite. 

 The analysis calculated on this basis gives fairly satisfactory 

 results. By assuming that all the protoxide of iron and 

 nickel is present as a constituent of magnetite, and that the 

 remaining sesquioxide and water are present as limonite, the 

 different constituents can be fully accounted for. Such a con- 

 stitution also explains the magnetic character and color of the 

 powder. Calculated in this manner and grouping the minor 

 constituents according to their apparent origin, the following 

 constitution of the shale is indicated : 



Limonite . . _ _ 52*99 



Magnetite ._ 42-39 



Schreibersite 0'64 



Graphite 0*15 



Lawrencite 0-14 



Aragonite 0'80 



Andradite 2*45 



Quartz 0'21 



99-77 



