266 



/. C. BRANNER 



known even in Europe, and it was altogether unknown in 

 America. 



At the time when it was found that this rock was bauxite 

 (1887) it was being used extensively for making the roadbed 

 of the Little Rock and Sweet Home turnpike, especially along 

 the part of the road near one of the bauxite beds. It had also 

 been recommended by a former state geologist, Mr. W. F 

 Roberts, Sr., as a " pisolitic iron ore," and attempts had been 

 made to mine some of the highly colored Saline county beds 

 for iron. 



Definition and compositioii. — It is practically impossible to 

 draw a sharp line of division between bauxite as defined miner- 

 alogically and what appears in a hand specimen to be the same 

 thing, but which on analysis is found to contain one or another 

 impurity in such proportions as to throw it out of the bauxite 

 list. Mineralogically bauxite is a hydrate of alumina,^ but it is 

 never found without certain impurities, the common ones being 

 iron, silica, potash, soda, and titanium. All these impurities are 

 found in the Arkansas bauxites, and in some cases the iron is so 

 abundant that the beds have been prospected with a view to 

 using the material as an ore of iron. The following analyses of 

 some of the more ferruginous varieties show its iron contents : 



ANALYSES OF FERRUGINOUS PISOLITIC BAUXITE. 



No. 4 was collected by the writer in 2 S. 14 W. section i, 

 northwest quarter ; the other numbers are from the Saline 



' St. Claire Deville regards it as a variety of Diaspore (AlgOgHgO) ; Dufrenoy 

 thinks it is close to Gibbsite (AI0O33H3O), while Liebrich shows it to be closely 

 related to or identical with Hydrargillite. 



