RAW MATERIAL: NATURAL-CEMENT ROCK. 203 



The series shown, from the top down, was as follows: 



Feet. 

 Blue limestone 8 



Slaty limestone (cement rock) 4 



Blue limestone 6 



* Argillaceous limestone 2 



* Siliceous limestone (hydraulic) 4 



* Siliceous limestone (cement rock) 7 



Fine black limestone 12 



Earthy limestone 3 



Shales 



When the plant was visited by the writer, in the fall of 1902, the 

 three beds marked with asterisks (*) were being worked for natural 

 cement. Spencer quotes the following analyses, made by W. J. Land: 



(1) (2) 



Silica (SiO 2 ) 22.10 10.00 



Alumina (A1 2 O 3 ) 5.45 6.10 



Iron oxide (Fe 2 O 3 ) 1-80 2.00 



Lime (CaO) 24.36 30.80 



Magnesia (MgO) 12.38 12.42 



Carbon dioxide (CO 2 ). 32 . 76 37.88 



Organic matter 0.15 . 50 



Water 1 .00 . 30 



Cementation Index 1 , 69 . 749 



Of these analyses, No. 1 probably represents the composition of 

 the 7-foot bed of cement rock noted in Spencer's section, while No. 2 

 is probably from the 4-foot bed of hydraulic limestone immediately 

 overlying this. As these beds are both worked for cement, the index 

 of the product lies between those of the two rocks. 



Illinois. Three natural-cement plants operated by two companies 

 are now working in Illinois, all of them being located near Utica, La 

 Salle County. The rock used is a limestone belonging to the so-called 

 " Lower Magnesian " group of early Western geologists. It is of 

 Ordovician age and underlies the St. Peter's sandstone. 



The section exposed in the neighborhood of the Utica cement-plants 

 is as follows from the top downward: 



Thickness. 

 Cement rock 7 feet 



Limestone 16-22 " 



Cement rock 6 " 



Sandstone 2-4 " 



Cement rock 5 " 



Of the three cement-rock beds shown in this section, the upper- 

 most bed gives a very quick-setting cement, while the two lower beds 

 furnish products of much slower set. 



