78 GEOLOGICAL SURVEY OF THE TERRITORIES. 



houses and other buildings by the Union Pacific Raih^oad. Near Chey- 

 enne City these same Tertiary beds yield an excellent limestone, which 

 has been much used at that place. These Tertiary rocks are rather porous 

 but work easily, and are sufiSciently durable in the absence of more 

 compact rock. 



Along the margin of the Laramie range, about 16 miles west of Chey- 

 enne City, there are beds of white limestone, of the Carboniferous age, 

 which, when burned into lime, is of the finest quality. The walls of 

 houses plastered with it are as white as snow, and it is a great favorite 

 with masons. The supply is inexhaustible. As soon as we reach the 

 mountains the building-materials are as extensive as the ranges them- 

 selves. The syenites i)redominate and are of every quality, from a com- 

 pact, fine-grained quality to a coarse aggregate of quartz and feldspar, 

 decomposing readily under atmospheric influences. 



I would here call the attention especially to some beds of fine-grained 

 compact syenite along the line of the Union Pacific Eailroad near the 

 summit of the first range, which nearly equals the best Scotch syenite 

 and resembles it very much. 



The Union Pacific Eailroad contemplate transporting this beautiful 

 syenite to Omaha, to construct with it the piers of the bridge across the 

 Missouri Eiver. A few years ago such a thought would have excited 

 surprise and perhaps ridicule as visionary, but now it is so feasible that 

 it ceases to be wonderful. I regard this syenite to be as durable and 

 more elegant for building-material than the Quincy granite. 



One of the most important problems for solution, aliecting the pros- 

 perity of this portion of the West, is the possibility of utilizing the vast 

 quantities of coal and iron with which this country abounds. All the 

 coals of Wyoming and Colorado appear to be of Tertiary age, and so 

 extensive are they in the West that it becomes a question whether the 

 Tertiary might not with more propriety be called the Carboniferous or 

 coal-bearing period. I have estimated the coal area north of the Arkan- 

 sas and south of the Lodge Pole Creek and east of the mountains at 

 5,000 square miles. It is quite possible that a more careful examination 

 will show that it covers a still larger area. 



In connection with this coal are large deposits of brown iron-ore or 

 limonite, which is easily reducible, and if the coal or lignite can be used 

 in smelting these ores, the iron as well as the coal will prove a source of 

 great revenue to the country. This iron-ore occurs in the form of nodules 

 or concretions, varying in size from an ounce to several hundred pounds 

 in weight. It resembles very closely the iron-ores of Maryland and 

 Pennsylvania. It seems to be co-extensive with the coal-beds, though 

 occurring more abundantly at some localities than at others. About 

 32 miles south of Cheyenne City there are large quantities, and, 

 within a few miles, beds of coal five or six feet in thickness are now 

 worked. At South Bowlder Creek it occurs again in great quantities, 

 scattered through 1,200 to 1,500 feet of sands and clays connected with 

 the coal. It will doubtless be found in the form of a carbonate of iron 

 beyond the reach of atmospheric influences. 



The finest smelting-furnace erected in Colorado was established there 

 by Mr. Joseph Marshall, and he informed me that it required about three 

 tons of the ore to make one ton of pig-iron. Over 500 tons of this ore 

 have been taken from this locality, and the area occupied by it is over 

 50 square miles. There are many other localities on both sides of the 

 mountains where this form of iron abounds, and it is safe to say that if 

 this mineral fuel, which abounds everywhere, can be made useful for 

 smelting purposes, these coal and iron ore beds will exert the same kind 



