I COLORADO. 123 
Analyses of limestones /rout Colorado west of the Front Range — Continued. 
No. 
Silica. 
(Si<>,,. 
33 
Alumina 
I \ l 2 3 ) 
iron oxide 
Trace. 
4. 
13 
.75 
1.00 
n. d. 
ii.d. 
31. 12 
.55 
2.04 
.15 
.82 
.07 
.36 
.17 
4.42 
.10 
.62 
.25 
7.91 
.32 
1.75 
.32 
2.69 
.21 
Lime 
(CaO). 
55. SI 
53. 00 
53. 40 
5)5. 20 
37. 28 
54. 62 
55. 47 
55. 58 
52. 97 
55. 24 
50.83 
53. 60 
54.23 
Magnesia 
(MgO). 
.16 
. 59 
.45 
n. d. 
.54 
.25 
.22 
.37 
.40 
.24 
.70 
1.23 
.21 
( 'arbou 
dioxide 
(C0 2 ). 
4-1.03 
42.28 
42.46 
n.d. 
29.88 
43. 28 
43. 86 
44.17 
42. 12 
43.81 
40.90 
43.65 
42.97 
9. Glenwood Springs, Garfield County. George Steiger, analyst. Bull. U. S. Geol. Survey No. 
p. 273. 
. North Park, Grand County. B. E. Brewster, analyst. Fortieth Par. Survey, vol. 2, p. 115. 
. Gunnison County. Ann. "Rept. Colorado School Mines for 1887. p. 21. 
. Morrison, Jefferson County. L. G. Eakins, analyst. Bull. U. S. Geol. Survey No. I(i8, p. 270. 
. Mount Silverheels, Park County. W. F. Hillebrand, analyst. Ibid., p. 272. 
. Fairplay, Park County. W. F. Hillebrand, analyst. Ibid. 
. Aspen, Pitkin County. L. G. Eakins, analyst. Ibid., p. 273. 
. Aspen Mount, Pitkin County. Reese & Richards, analysts. Rept. Colorado School Mines, 1886, 
7. 
. Aspen Mount, Pitkin County. F. Bardwell, analyst. Ibid. 
. Aspen Mount, Pitkin County. F. Buckley, analyst. Ibid., p. 68. 
. Aspen district, Pitkin County. George Steiger, analyst. Bull. U. S. Geol. Survey No. 168, p. 272 
. Jacque Mount, Tenmile district, Summit County. W. F. Hillebrand, analyst. Bull. U. S. Geol. 
vey No. 168, p. 274. 
. Nea i' Sal. hath Rest tunnel, Tenmile district, Summit County. W. F. Hillebrand, analyst. Ibid. 
. Searls Gulch, Tenmile district, Summit County. W. F. Hillebrand, analyst. Ibid. 
. North of Sugarloaf, Tenmile district, Summit County. W. F. Hillebrand, analyst. Ibid. 
j25. Pittston tunnel, Tenmile district, Summit County. VV. F. Hillebrand, analyst. Ibid. 
. Summit quarry, Tenmile district, Summit County. W. F. Hillebrand, analyst. Ibid. 
. Fletcher shaft, Copper Mountain, Tenmile district, Summit County. W. F. Hillebrand, analyst. 
LIMESTONES EAST OF THE FRONT RANGE 
[n the eastern portion of Colorado the surface rocks are of Creta- 
)us or later age. While mostly made up of clays and sands, these 
ks contain one limestone formation of great importance as a possi- 
source of Portland-cement material. This is the Niobrara limestone 
the Cretaceous. 
The areas in which the Niobrara limestone outcrops in eastern Col- 
ido, as shown on the Hayden map, may be described as follows: 
One belt of Niobrara limestone enters Colorado from Nebraska, fol- 
ding the South Platte and ending between Fort Morgan and Greeley, 
lother belt enters the State from Wyoming, at a point just west of 
e Colorado and Southern Railroad, and runs about due south, as a 
nd from 1 to miles in width, the towns of Laporte, Namaqua, and 
