DENVER & RIO GRANDE WESTERN ROUTE. 



191 



Although the shale which forms the valley that the traveler has 

 been following from. Grand Junction to this place, if he came over 

 the main line, or from Montrose, if he came over the narrow-gage 

 line, continues along the foot of the Book Cliffs to the region beyond 

 Green River in Utah, the railroad does not follow it because near 

 the State line it ceases to form a valley and the outcrop is rough and 

 is broken by stream valleys that cross it. In order to avoid this 

 rough country the railroad turns to the south (left) soon after leav- 

 ing Mack and follows the river through Ruby Canyon for a distance 

 of more than 18 miles. The gap in the ridge through which the rail- 

 road reaches the river can be seen on the left from the station. 



Half a mile beyond Mack the railroad swings sharply to the 

 south (left) and leaves the shale valley. It cuts through the sand- 

 stone rim that bounds the valley on the south nearly at right angles," 

 disclosing the sandstones and variegated shale beds that underlie 

 the dark shale (Mancos) of the main valley. The first sandstone 

 to be seen is the Dakota, the lowermost formation of the Upper Cre- 

 taceous. Underlying the Dakota is the McElmo formation, equiva- 

 lent to the upper part of the Gunnison formation, which has already 

 been seen at a number of places. The McElmo formation has every- 

 where about the same character and when once recognized is easily 

 identified wherever it is seen. It includes an upper member 150 

 feet thick — the one that is first seen after leaving Mack — composed 

 of variegated shale and sandstone, which on account of its relative 

 softness weathers back into gentle slopes. The underljdng member 

 is about 60 feet thick and consists mainly of sandstone, which is more 

 resistant to weathering than either the overlying or the underlying 

 shale and therefore stands out and makes terraces or benches on the 

 hillsides. The sandstone is in turn underlain by a gray clay or 

 shale, which has a thickness of about 100 feet. These rocks form the 

 canyon walls for a distance of about 2 miles, but they are so soft 

 that in no place are the walls very steep. Owing to the red and 

 green tints, the color effect is rather pleasing, but it soon becomes 

 monotonous, and some other color or larger masses of color would 

 make a welcome change. 



easily mined with a hand pick and is 

 placed in large bags to be hoisted to 

 the surface ready for shipment to mar- 

 ket. The veins are rarely more than 

 10 feet in width, but they extend to 

 unknown depths and in some places 

 have been mined to a depth of 200 to 

 300 feet below the surface. The 

 miners take special precautions to pre- 

 vent fire, for the gilsouite dust is ex- 

 tremely explosive. No artificial lights 



are used in the mines, even at great 

 depths. 



The entire gilsonite output of Utah 

 (about 20,000 tons annually) is hauled 

 over the narrow-gage Uintah Railway 

 to Mack, where it is reloaded to the 

 larger cars of the Denver & Rio Grande 

 Western Railroad. 



Gilsonite is extensively used in the 

 manufacture of paints, varnishes, roof- 

 ing materials, and rubber substitutes. 



