228 
CEMENT MATERIALS AND INDUSTRY. 
[BULL. 24M 
:;: 
massive beds flank the great ranges of the State and form its mo 
picturesque scenery. The overlying Jurassic limestone is argillaceov 
and of uncertain development. The Devono-Silurian limestones are 
impure, while the Cambrian limestones are thin bedded and usually not 
uniform in composition. 
The limestones are found along the northern slope of the mountain 
front from Red Lodge, in Carbon County, westward to Livingstoil 
northward about the flank of the Bridger and Little Belt and Bell 
ranges to the Main range west of Great Falls. Practically all til 
southern ranges of the western part of the State are uplifts with cor« 
of gneiss or granite mantled by limestones of various ages. Such 
rocks occur westward almost to the Bitterroot Valley. 
North of the line of the Northern Pacific Railroad the Carboniferoui 
limestones soon disappear, though the Cambrian rocks form the mount 
tain summits almost to the Canadian line. The northwestern part m 
the State, however, is composed mostly of Algonkian rocks, mostli 
argillaceous. A series of oolitic limestones, the Newland limestonji 
forms a constant feature of this Belt terrane, but nothing is known H 
the composition of these rocks save that they are usually quite j 
argillaceous. r 
The following analyses of Montana limestones are on record: 
Analyses of limestones, Montana. 
_,* 
Silica (Si0 2 ) 
Alumina (A1 2 3 ) 
Iron oxide (Fe 2 :! ) . . 
Lime (CaO) 
Magnesia (MgO) 
Carbon dioxide (C0 2 ' 
1.45 
.16 
.76 
49.42 
2.74 
41.73 
0-4 s 
4.4 
.2 
52. 1 
1.0 
42.0 
1. Persell Limestone Company, near Helena. E. Starz. analyst. 
2. Montana Marble and Mining Company, near Helena. C. M. Fassett, analyst. 
Both of the above analyses, but particularly the first, represer 
limestones whose composition would be very satisfactory from thlj 
Portland cement manufacturers' point of view. 
