322 GEOLOGICAL SURVEY OF THE TERRITORIES. 



DESCRIPTION OF LOCALITIES. 



Colorado. — Coal has been found in Colorado both on the east and west 

 sides of the Platte Elver; but the only mines of importance are near 

 the eastern foot of the easternmost or Blue Hills range of the mount- 

 ains. Ihe formation to which they belong is a series of sandstones and 

 fire-clay, probably of lower tertiary age, which ranges north and south, 

 and along its western margin is found uptilted in a vertical position, 

 and sometimes dipping toward the metainorphic rocks that make up 

 the steep mountain slope not half a mile distant. Farther away from 

 the mountains the inclination is eastward, and so gentle that the coal 

 strata overspread large tracts of country. The formation follows the 

 range of the mountains north and south to an undetermined extent, 

 and coal is met with in it for more than a hundred miles from Denver 

 in each direction; but the only mines of value, excepting a few to the 

 south, are at Golden City, fifteen miles west from Denver, and thence 

 north for ten to fifteen miles into Boulder County, along the banks of 

 the creeks that descend from the mountains eastward toward the Platte. 



Golden City. — The first discoveries of coal at this place were several 

 small and nearly vertical beds near together in the steep bank of Clear 

 Creek, about half a mile below where it passes out from the mountains. 

 These were followed but a short distance under the bank toward the 

 south, when the extension of one of the beds in this direction was 

 opened at the summit of the ridge, a quarter of a mile from the creek. 

 The bed was here found so large — from ten to fourteen feet thick — that 

 the lower workings were abandoned, and a vertical shaft was sunk on 

 the hill, one hundred feet deep in the coal bed, and levels have been 

 driven north and south from the bottom, and also fifty-six feet below the 

 surface. The bed proved to be very irregular in thickness, sometimes 

 pinching in to a few inches and then expanding to eight or ten feet. 

 Its average thickness is not probably more than five feet. A small 

 steam-engine is used for pumping and hoisting. Little water, however, 

 is encountered. A cross cut from the bottom, driven seventy feet east, 

 penetrated the following strata : clay, 4 feet thick ; sandstone, 4 ; coal, 2 ; 

 sandstone, 12; clay, 3; sandstone, 7; clay, 8; black slate, 3; clay, 4; 

 sandstone, 3} clay, 2; coal, 2 ; clay, 8; coal, 2; sandstone, 6. The last 

 stratum is probably the extension below of a heavy ledge of sand- 

 stone that forms the crest of the ridge. The clay is all fire-clay, of 

 pretty uniform and excellent quality, very similar in appearance to that 

 of the true coal-measures. It seems to be the prevailing material of 

 the formation, and is used for the manufacture of fire-brick in an exten- 

 sive manufactory at the base of the hill. The coal mine has been worked 

 only to the moderate extent of about ten tons a day, for the supply 

 chiefly of the local demand. The appearance of the coal itself — of a 

 dull black without the bright luster common to the coals from the other 

 mines — has operated unfavorably to its reputation in the Denver mar- 

 ket, though no inferiority of quality is indicated by the analyses. It is 

 obtained, too, in pieces of very irregular shape, quite unlike the hand- 

 some rectangular blocks of the other coals. Like them, however, it is 

 almost entirely free from slate and iron pyrites. Besiu occurs in it in 

 scattered particles and bunches more abundantly than in the coals of 

 Ihe other mines. It may, perhaps, prove a better coal for gas than the 

 other mines afford, which will soon be ascertained, if it has not been 

 already, at the new gas works at Denver. The locality is very favorably 

 situated for supplying the mining towns in the mountains with fuel, so 

 «oon as the railroad now in progress up the gorge of Clear Creek reaches 



