THE STONE FOR FLUXES. 27 



On the Plateau Region of the Warrior Field ; by Henry Mc- 

 Calley. 



On the Warrior Basin, by Henry McCalley. 



On the Cahaba Coal Field, by Joseph Squire ; On tb<* Coosa 

 Coal Field, by A. M. Gibson. 



THE STONE. 



LIMESTONES AND DOLOMITES. 



These rocks which are used for furnace flux and for lime 

 burning are to be found in Alabama in sufficient quantity to 

 satisfy every demand that will ever be made on them. 



The fluxing rocks in all the furnaces of the state were exclu- 

 sively limestones until a few years ago, when dolomite was 

 found to be well adapted to the purpose, and it has since come 

 into very general use in the Birmingham district, where it exists 

 in very convenient proximity to the furnaces. The dolomite as 

 a rule, is of more uniform composition and freer from silica 

 than the limestones, that used in the Birmingham furnaces hold- 

 ing on an average not more than 1.5 per cent, silica, while the 

 limestone will generally average 3 to 4 per cent. The dolomite 

 is therefore better for the making of low silicon pig iron. The 

 purest of the limestone beds are however purer than the best o<f 

 the dolomite, but the interstratification of ledges o>f varying 

 quality necessitates much careful selection in quarrying. 



The use of limestone as a flux is now again on the increase be- 

 cause of demand for the slag for cement making. 



Dolomite.' The most important horizon of the dolomite is 

 the Knox Dolomite of the Cambrian, while the limestones be- 

 long mostly to the Trenton of the Lower Silurian and to the 

 Mountain Limestone division of the Lower Carboniferous. All 

 of these have been very extensively quarried to supply the fur- 

 naces. 



The Knox Dolomite as a formation is from 2,000 to 5,000 feet 

 in thickness, the lower part containing some beds of exceedingly 

 pure dolomite, while in the upper part this dolomite is very much 

 intermixed with chert. 



The rock used as flux is mostly coarse grained, light gray to 

 dark blue in color, and more or less crystalline in texture. 



