212 



CEMENTS, LIMES, AND PLASTERS. 



TABLE 99. 

 ANALYSES OF NATURAL-CEMENT ROCK, LEHIGH DISTRICT, PA. 



1. Siegfried, Pa. Mineral Industry, vol. 1, p. 49. 



2. Coplay, Pa. Mineral Industry, vol. 1, p. 49. 



3. Lehigh district. Quoted by C. Richardson. Brickbuilder, vol. 6, p. 151. July, 1897. 



4. Average of preceding three analyses. 



Texas natural-cement plant. It is obvious that, if this statement be 

 correct, the product obtained by burning a rock of such composition 

 cannot be a natural cement in any proper use of the term. It would, 

 in fact, be merely a very weak hydraulic lime. 



ANALYSIS OF NATURAL-CEMENT ROCK, TEXAS. 



Silica (Si0 2 ) 5.77 



Alumina (A1 2 O 3 ) . . . . 



Iron oxide (Fe 2 O 3 ) 



Lime (CaO) 50.45 



Magnesia (MgO) . 28 



Virginia. For many years natural cement has been burned near 

 Balcony Falls, Rockbridge County, Va. The rock used is a clayey 

 magnesian limestone of Cambrian age, closely related geologically and 

 technologically to that described below as being used in West Virginia. 



TABLE 100. 

 ANALYSES OF NATURAL-CEMENT ROCK, VIRGINIA. 



2.14 



1. Balcony Falls. E. C. Bovnton, analyst. Gillmore. "Limes, Cements, and Mortars", p. 125 



2. Balcony Falls. C. L. Allen, analyst. "The Virginias", vol. 3, p. 88. 



3. Average of preceding two analyses. 



