484 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



[vol. so 



VI. The Iron Shale and Shale Balls 



Occurrence, Composition, and Origin. — Scattered over the surface 

 of the plain, and practically coextensive with the iron, are abundant 

 fragments and nodules of brown iron oxide, sometimes stained green- 

 ish from the presence of a nickel hydroxide. These, as a rule, have 

 a somewhat shaly or platy structure, the plates sometimes slightly 



Fig. 128. 



curved, or again, and more rarely, are in the form of flattened ovals 

 sometimes pear-shaped, and invariably deeply cracked and fissured 

 (fig. 128). These shale fragments were noted by Foote in 1891 

 and their probable connection with the iron suggested. The oval 

 "shale balls" were, however, first noted by Mr. Barringer. That 



