THE OXIDATION OF METEORIC IRONS WITH COM- 

 PARATIVE DESCRIPTIONS OF TWO NEW EXAMPLES 

 OF MAGNETIC IRON OXIDES FROM TERRESTRIAL 

 SOURCES 



By Earl V. Shannon 

 Assistant Curator of Geology, United States National Museum 



INTRODUCTION 



Meteorities are divided into three major subdivisions, briefly tlie 

 irons, the stony irons, and the stones. These differ from each other 

 in degree rather than in kind and all contain more or less iron in the 

 form of a crystalline metallic alloy with an average content of nickel 

 not far from 10 per cent. The nickel is accompanied by only minor 

 amounts of other elements, which include cobalt, copper, phosphorus, 

 and platinum, usually in amount in the order named. Many such 

 have been seen to fall, and from the number and weight of those 

 known to have reached the earth in historic times it is certain that 

 the total number which has fallen throughout geologic ages is enor- 

 mous. However, like a lump of ordinary manufactured iron or steel 

 exposed to atmospheric agencies, the metal of meteorites is subject 

 to rapid alteration and their forms and identities are soon lost by 

 mechanical and chemical disintegration. The meteorities are even 

 more prone to chemical alteration, under the influence of the weather, 

 because of the fact that they almost invariably contain some ferrotis 

 chloride, which hastens the change, as has been pointed out repeatedly. 

 Of those iron meteorites which have fallen during geologically 

 recent times the very latest have almost invariably a very thin oxide 

 scale or crust. Those of intermediate age may consist of oxide 

 masses inclosing cores of unaltered metal, while the older are en- 

 tirely oxidized and hydrated and their provenance is only established 

 by the presence of minor constituents or an inherited structure. 



The earliest published reference to the nature of the oxidation prod- 

 ucts arising from the alteration of meteoric iron appears to have been 



No. 2717.— Proceedings U. S. National Museum, Vol. 72, Art. 21. 



58972 — 27 1 



