THE LESSER METALS. 



265 



region, where the ores occur with Lower Silurian cherts. There 

 are numerous other localities not yet of commercial importance 

 along the Appalachians, in Tennessee and elsewhere. Full de- 

 scriptions will be found in Penrose's report, cited below. 



2.14.16. Batesville, Ark. The ore is braunite, and is found in 

 masses disseminated in a residual clay left by the alteration of a 



FIG. Q5.The Turner mine, Batesville region, Arkansas. After B, A. F. 

 Penrose, Geol. Survey Ark,, 1890, Vol. L, p. 272. 



limestone locally called the St. Clair. It is of geologic age be- 

 tween the Trenton and Niagara periods, and is underlain by 

 another limestone called the Izard, which is later than the Calcif- 

 erous. On the St. Clair a series of cherts called the Boone cherts 

 is found, which is of Subcarboniferous (Mississippian) age. The 

 clays are sometimes in valleys, sometimes on hillsides, according 

 to the unequal decay of the limestone. South of the Bates- 

 ville district are the Boston Mountains, a range of low hills 500 



