Mance: Quarry Industry of Southern Indiana 193 



powers of the two carbonates are to each other as 84 is to 100, so reducing 

 the magnesia carbonate to its equivalent in fluxing power of lime carbonate, 

 we have 43 ^ -^qq 



h 51 = 102.19 



84 



Therefore the relative value of the two fluxing materials of this district are 

 to each other as 88 is to 102.19. 



In other words, the dolomite flux is preferred because of 

 its greater purity, but this excuse will not apply to the waste 

 limestone of Southern Indiana quarry districts since none of the 

 dolomites used for flux is any freer from impurities than the 

 Oolitic limestones which often carry as high as 98.5 per cent 

 calcium carbonate. The overlying Mitchell limestone is, if 

 anything, purer than the Oolitic stone. 



Another argument in favor of dolomite fluxing stone is that 

 it gives a more liquid slag than a limestone fluxing stone. On 

 this point I would say that very liquid slags are only necessary 

 where the ore used contains a large quantitj^ of impurities; and 

 that the onh^ blast furnaces that could use our waste stone, on 

 account of the high freight rates, are those located around Gary 

 and Chicago, which use much higher grade ores than those 

 demanding highly liquid slags. 



Dolomite cannot be used as a slag when the ores run high 

 in sulphur. In such cases the hme carbonate is better than mag- 

 nesium carbonate because the calcium has a greater affinity for 

 sulphur than has magnesium. 



Since most of the ores now coming from the ore fields of Mich- 

 igan and Minnesota are high-grade ores carrj^ng some sulphur^ 

 the demand for limestone slag is sure to increase, even if the manu- 

 facture of blast furnace cement does not increase. This latter 

 industry is, however, developing rapidly in manj^ foreign countries, 

 and seems almost sure to increase in this country because the cost 

 of m.anufacture is very small and it offers an opportunitj^ for the 

 profitable disposal of a large amount of waste materiaL 



Waste stone has been sent out of the Southern Indiana quarry 

 district for use as flux in the steel mills of Gary and Chicago 

 for a long time: but the amount has been small and the benefit 

 to the quarryman from this source has been httie more than 

 that of getting their waste piles out of the way. This condition 

 results from the excessive freight rates charged by the railroads, 

 or, at least, the adverse conditions under which shipments must 



13 



