CKTCL. | 
IOWA. 
153 
le Niagara. About midway the rock has been extensive^ quarried, 
t Independence and Waterloo, where it is a soft, easily crushed lime- 
bone, apparently nonmagnesian in character. At Waverly the rock 
; soft, thin bedded, and exposed to a total thickness of about 50 feet, 
nalysis of two separate beds, by Lundteigen, gave the following 
esults: 
Analyses of Devonian limestone at Waverly. 
46. 34 
} 19. 90 
lica (Si0 2 ) 
lumina ( A1 2 3 ) .' 
on oxide ( Fe 2 3 ) 
pme (CaO) 10. 27 
agnesia (MgO) 2. 00 
ilphnr trioxide (S0 3 ) 01 
oss on ignition 
13.90 
92.42 
2.25 
1.32 
49. (it; 
3.24 
.00 
42.80 
99.27 
Still farther north, in Mitchell County, the limestone has attracted 
Mention because certain beds are lithographic." The following anal- 
sis, -made b} T Mr. A. B. Hoen, suggests that at least some of the stone 
i sufficiently free from magnesia to be suitable for cement material. 
Analysis of Devonian limestone, Mitchell County. 
lica (SiO a ) 0. 78 
lumina (A1 2 3 ) 12 
ime (CaO ) 54. 91 
Magnesia (MgO) 07 
)da ( Na 2 ) 18 
otash (K 2 0) ' 11 
arlxui dioxide (C0 2 ) 43. 16 
pater (H 2 0) 35 
There are a number of fine exposures showing a thickness of 10 to 
5 feet of the nonmagnesian beds. Not all of this rock is free from 
racks and crystals, but it is all similar in composition to the sample 
paly zed. At the (Table and other quarries there is practically no 
gripping, while in the vicinity is an abundance of loess clay. 
LIME CREEK SHALES. 
DISTRIBUTION. 
The uppermost member of the Devonian section of Iowa is well dis- 
played in Cerro Gordo County, and has been discussed and mapped in 
" Iowa Geol. Survey, vol., 13, pp. •.'92-352. 
