62 Field Columbian Museum — Geology, Vol. III. 



IRON METEORITES. 



These are meteorites consisting essentially of nickel-iron. Most 

 of them contain, in addition, an appreciable amount of sulphides, car- 

 bides, and phosphides, but the presence of silicates in quantity removes 

 a meteorite from this class. The iron meteorite of Tucson contains 

 about five per cent of forsterite, and the meteorites of Kodaikanal, 

 Persimmon Creek, and Tula also contain silicate aggregates, but in 

 small quantities. In general, it may be said that if the quantity of 

 silicate grains exceeds five per cent the meteorite is not considered 

 as belonging to the class of iron meteorites. About two hundred and 

 fifty iron meteorites are now recognized, the exact number being in- 

 determinate on account of differences of opinion as to identity of 

 origin in several cases. The chief divisions of iron meteorites, accord- 

 ing to the Rose-Tschermak-Brezina classification, are hexahedrites, 

 octahedrites, and ataxites. These are sub-divided as follows: 



CLASSIFICATION OF IRON METEORITES ACCORDING TO 

 ROSE, TSCHERMAK, BREZINA, AND COHEN 



I. Hexahedrites. 



A. Normal hexahedrites. 



B. Brecciated hexahedrites. 

 II. Octahedrites. 



A. Normal octahedrites. 



1. Coarsest octahedrites. 



2. Coarse octahedrites. 



3. Medium octahedrites. 



4. Fine octahedrites. 



a. Prambanan group. 

 />. Rodeo group. 



5. Finest octahedrites. 



a. Salt River group. 



(^. Tazewell group. 



c. Cowra and Victoria \Vest. 



B. Hammond octahedrites. 



C. Brecciated octahedrites. 

 III. Ataxites. 



A. Nickel-poor ataxites. 



1. Si rati k group. 



2. Nedagolla group. 



3. Rafruti group. 



