32 
CEMENT MATERIALS AND INDUSTRY, 
Analyses of Lehigh district cement materials. 
Lbull. 243. 
Silica (Si0 2 ) 10. 02 
Alumina ( AL0 3 ) ) n 
v " " \ 6.26 
Iron oxide ( Fe 2 3 ) J 
Lime carbonate (CaC0 3 ) ; 78. 65 
Magnesium carbonate (MgC0 3 ) . . 4. 71 
Cement rock. 
9.52 
4.72 
80.71 
4.92 
14.52 
6.52 
73.52 
4.69 
16.10 
2.20 
76.23 
3.54 
Limestone. 
3.02 
1.90 
3.04 
1.98 
0.70 
92.05 95.19 
2.03 
"cement rock" in other parts of the united states. 
Certain Portland-cement plants, particularly in the western part of 
the United States, use combinations of materials closely similar to 
those in the Lehigh district. Analyses of the materials used at several 
of these plants are given in the following table: 
Analyses of "cement rock" and limestone from the western United States. 
Utah. 
Silica (Si0 2 ) 
Alumina (A1 2 3 ) 
Iron oxide (Fe 2 3 ) 
Lime carbonate (CaC0 3 ) 
Magnesium carbonate ( MgC0 3 ) . . 
Cement 
roek. 
21.2 
8.0 
62.08 
3.8 
Lime- 
stone. 
3.0 
89.8 
0. 7( 
California. 
Cement 
rock. 
20.06 
10.07 
3.39 
63. 40 
1.54 
Lime- 
stone. 
7.12 
2.36 
1.16 
87.70 
0.84 
Colorado. 
Cement, 
rock. 
14.20 
5.21 
1.73 
75.10 
1.10 
Lime- 
stone. 
88.0 
In addition to these "cement rocks" many of the chalky limestones 
discussed on pages 33-34 are sufficiently argillaceous to be classed as 
"cement rocks." Because of their softness, however, all the chalky 
limestones will be described together. 
PURE HARD LIMESTONES. 
Soon after the American Portland-cement industry had become 
fairly well established in the Lehigh district attempts were made in- 
New York State to manufacture Portland cement from a mixture of 1 
pure limestone and clay. These attempts were not commercially suc- 
cessful, and although their failure was not due to any defects in the 
limestone used, a certain prejudice arose against the use of the hard 
limestones. In recent years, however, this has disappeared, and a 
very large proportion of the American output is now made from mix- 
tures of limestone with clay or shale. The use of the hard limestone 
is doubtless due in great part to recent improvements in grinding 
machinery, for the purer limestones are usually much harder thac 
