RAW MATERIAL: NATURAL-CEMENT ROCK. 221 



As the rock will lose from 25 to 40 per cent of weight during the process 

 of burning (averaging about 33 J per cent), the cost per ton of burned 

 rock will vary from 30 to 90 cents. Reducing this to terms of barrels 

 of cement, the cost of raw material per barrel of finished cement may 

 range from 4 to 13 cents. 



After the raw material has been excavated, no preliminary treat- 

 ment is strictly necessary before sending it to the kilns. It is advisable, 

 however, to feed the kilns with lumps of approximately equal size, 

 because if the charge consists of a mixture of large and small masses 

 of rock the latter will be overburned before the former are properly 

 calcined. In most plants this rough sizing is accomplished by sledging 

 the larger pieces at the quarry. A few plants, however, use crushers, 

 one installation being illustrated in Fig. 36. 



References on natural- cement rock. The natural-cement rocks of 

 the various states are described more fully in the reports and papers 

 listed below. For convenience these have been arranged by States in 

 alphabetical order. 



UNITED STATES in general. Eckel, E. C. Cement materials and cement 

 industry of the United States. Bulletin 243, U. S. Geolog- 

 ical Survey. 1905. 



Gillmore, Q. A. Limes, Cements, and Mortars. 

 Richardson C. Limes, hydraulic cement, mortar, and con- 

 crete. Brickbuilder, vol. 6, pp. 151-153, 175-179, 202-204, 

 228-229. 1897. 



CALIFORNIA. Grimsley, G. P. The Portland-cement industry in California. 

 Engineering and Mining Journal, July 20, 1901. 



CONNECTICUT. Lowrey, T. Water cement of Southington, Conn. Amer. 

 Journal of Science, vol. 13, pp. 382-383. 1828. 



FLORIDA. Cummings, U. Natural-cement rock in Florida. 20th Ann. 



Rep. U. S. Geol. Survey, pt. 6, pp. 549-550. 1899. 



GEORGIA. Cummings, U. Natural-cement rock at Rossville, Ga. 21st 



Ann. Rep. U. S. Geol. Survey, pt. 6, pp. 410-411. 1901. 

 Spencer, J. W. The Paleozoic group of Georgia. Report 

 Georgia Geol. Survey. 



ILLINOIS. Freeman, H. C. The hydraulic-cement works of the Utica 



Cement Co., La Salle, 111. Trans. Amer. Institute Mining 

 Engrs., vol. 13, pp. 172-181. 1885. 



INDIANA-KENTUCKY. Siebenthal, C. E. The Silver Creek hydraulic limestone 

 of southeastern Indiana. 25th Ann. Rep. Indiana Dept. 

 Geology, pp. 331-389. 1901. 



KANSAS. Haworth, E. Hydraulic cement in Kansas. Mineral Resources 



of Kansas for 1897, pp. 66-69. 1898. 



