220 



CEMENTS, LIMES, AND PLASTERS. 



plant in Georgia, a number of those in the Louisville district, and several 

 others work open quarries. 



This difference in general practice, taken in connection with differ- 

 ences in labor costs, etc., causes a wide variation between different 

 plants in the total cost of raw material delivered at the kilns. 



Open quarries can be readily worked at costs of from 20 to 35 cents 

 per ton of rock. In most cases the question of handling stripping 

 economically is more important than the costs of actual quarrying. 

 At one of the Louisville district plants, where hoists are used in the 

 quarry (Fig. 35) for loading the cars, the stripping is removed by scrapers 

 whose power is derived from these hoists. 



In an area such as the Rosendale district, where practically all the 

 cement rock is won by mining, costs will naturally be higher than where 

 open quarries are operated. At one of the largest mills the rock can 

 be delivered on top of the kilns for a trifle under 50 cents per ton. I 

 am informed that at another large mill, rock was mined for a series of 

 years at a cost of about 35 cents per ton. 



FIG. 36. Crusher for raw rock at Speed mill, Speeds, Ind. 



Summing up these considerations, it is probably within safe limits 

 to say that the cost per ton of rock may vary from about 20 cents in 

 a well-managed quarry to perhaps 60 cents or even more in a mine. 



