154 CEMENT MATERIALS AND INDUSTRY. [pill. 2 
Calvin's report on that area. He gives the following general secti 
of the formations: 
General section of the Lime Creek shales. 
1. Calcareous beds, light gray in color 
2. Magnesian shales and argillaceous dolomites 
3. Limestone with slender Idiostroma 
4. Fossiliferous calcareous shales 
5. Yellow nonfossiliferous shales 
6. Blue nonfossiliferous shales 
Nos. 4, 5, and 6 of this section make up the Hackberry member 
the formation, while the remaining beds represent the Owen beds. 
COMPOSITION. 
The shales constituting the lower portion of the foregoing secti 
are used at Mason City for the manufacture of clay goods and are r 
resented in the following analysis made by G. E. Patrick. 
Analysis of Lime Creek clay at Mason City. 
Silica (Si0 2 ) 54 
Alumina ( A1 2 3 ) 14 
Iron oxide (calculated as Fe 2 3 ) 
Maganese oxide (calculated as MnO ) 
Lime ( CaO ) 
Magnesia (MgO) .' 
Soda (Na 2 0) 
Potash (K 2 0) 
Carbon dioxide (C0 2 ) 4 
Hygroscopic water (expelled at 1 00° C. ) 
Combined water (expelled by ignition) c 
Total 9< 
This analysis represents only the noncalcareous portion. The b 
above contain considerable lime, as noted in the section given. In 
vicinity of Mason City, where these beds outcrop, there are extens 
exposures of the nonmagnesian beds of the underlying Cedar Vail 
and it should be possible to combine the two to advantage. 
CARBONIFEROUS LIMESTONES. 
Carboniferous rocks underlie a large portion of Iowa. They incl 
limestones, sandstones, shales, and coals. The limestones are v 
rarely magnesian, and because of this fact, as well as their excel] 
situation with reference to fuel and transportation facilities, it set 
not improbable that time will see the development of a considers 
cement industry based upon them. 
a Geology of Cerro Gordo County; Iowa Geol. Survey, vol. 7, pp. 117-192. 
