AET. 21 OXIDATION OF METEORIC IRONS SHANNON 13 



scopic examination showed the sample prepared for analysis to con- 

 tain a considerable amount of finely granular quartz as the only 

 notable impurity. The partial analysis made in the museum labora- 

 tory gave the following results: 



Analysis of ferromagnetic ocher 



Insoluble (quartz) 17.80 



Fe^Os 72. 20 



FeO 1. 64 



AI2O3 1 3. 12 



CaO Trace. 



NiO None. 



H2O above 110°C 2.80 



H2O below 110°C 1.10 



Undetermined 1. 34 



100. 00 



Mineralogically interpreted as in the above, this analysis gives: 



Quartz 17. 80 



Fe203 46. 07 



Limonlte (2Fe203.3H20) 26.38 



Magnetite (FeO.Fe.Os) 5.29 



AI2O3 3.12 



Loss 1. 34 



100. 00 



This interpretation indicates that not more than 5.29 per cent 

 of magnetite can be present so that the strongly magnetic and 

 polarized character of the material can not be attributed to this con- 

 stituent either as mechanically admixed magnetite or as magnetite 

 present in solid solution in hematite. 



This appears to be a rather good example of ferromagnetic ferric 

 oxide of natural origin. The 3.90 per cent of water tabulated in the 

 analysis actually represents loss on ignition and may include some 

 carbon dioxide or other volatile material. Although this amount of 

 water is equivalent to 26.38 per cent of limonite of an assumed com- 

 position of 2Fe203.3H20, it is doubtful that any such amount of 

 limonite is present. Any material of such fine grained structure is 

 bound to hold some hygroscopic water and the alumina indicated in 

 the analysis is probably present as a clay which may be highly 

 hydrous. 



Although no information as to the occurrence or origin of this 

 material could be obtained it seems unquestionably native and not 

 produced by the heating or other treatment of any of the other forms 

 of iron oxide. The subject of ferromagnetic ferric oxide has been 

 thoroughly discussed by Sosman and Posnjak,^^ their studies being 



^8 Robert B. Sosman and E. Posnjak. Iferromagnetic ferric oxide, artificial and natural. 

 Joiirn. Wash. Acad. Sci., vol. 15, No. 14, pp. 329-342, Aug. 19, 1925. 



