326 



CEMENTS, LIMES, AND PLASTERS. 



siderable magnesia (as compared with other Portland-cement materials) 

 throughout its entire thickness, and few analyses will show less than 

 4 to 6 per cent of magnesium carbonate. The following series of 

 analyses is fairly representative of the lower, middle, and upper beds 

 of the formation. The specimens from the upper beds, near the Hud- 

 son shales, show considerably less lime and more clayey matter than 

 those from the lower parts of the formation. 



TABLE 150. 

 ANALYSES OF TRENTON LIMESTONE (LEHIGH CEMENT ROCK). 



Ann. Kept. New Jersey State Geologist for 1900, p. 95. 



The specimens whose analyses are given above were mostly from 

 the vicinity of Belvidere, N. J., and, though representative in other 

 respects, seem to have been rather lower in magnesia than the usual 

 run of the Trenton limestone in the Lehigh district. 



Kittatinny magnesian limestone. Underlying the cement-rock series 

 is a very thick formation consisting of light-gray to light-blue massive- 

 bedded limestone, with frequent beds of chert. These limestones are 

 predominantly highly magnesian, though occasionally beds of pure 

 non-magnesian limestone will be found in the series. The magnesian 

 beds are, of course, valueless for Portland-cement manufacture, but 

 the pure limestone-beds furnish part of the limestone used in the Lehigh 

 district for addition to the cement. rock. An excellent example of this 

 is furnished by the quarry near the east bank of Lehigh River, just 

 above Catasauqua. In this quarry most of the beds are highly mag- 

 nesian, and are therefore useful only for road metal and flux; but a 



