WAGON WHEEL GAP

Wagon Wheel Gap mine. This property, which was owned by the American Fluorspar Co. until July, 1924, and then bought by the Colorado Fuel & Iron Co., is on the east side of Goose Creek directly opposite the Mineral Hot Springs, and is 14 miles south of Wagon Wheel Cap station, the shipping point on the Denver & Rio Grande Railroad. The property was first opened about 20 years ago by prospectors who mistook the fluorite outcrop for amethyst quartz or an extension of the amethyst vein at Creede. In 1911 the mineral was recognized as fluorspar and mining operations commenced. By 1913 development had progressed so far that 5,000 tons of ore was shipped in that year. During 1914 the mine was idle. It was reopened in 1915 and was worked intermittently until March, 1921, when it was closed for at least a year.

Past production.-Total fluorspar shipments up to 1921 are reported to have been 40,000 to 45,000 tons. The maximum production was reached in 1918, when 13,892 tons were shipped. In 1920, 12,000 tons were shipped, including 2,800 tons of high-grade, hand-picked lump, analyzing approximately 96.93 per cent CaF2, 2.64 SiO2, and 0.27 CaCO3, nearly all of which went to the Aluminum Ore Co. In 1921 the total shipment, 2,828 tons of fluxing gravel, was sent to Pueblo, Colo. No shipments were made in 1922, up to April, but the gravel stock pile at the mill has been sold.

Ore deposit.-The Colorado Geological Survey 25 says that the vein which is exposed on the steep hillside east of Goose Creek may be traced about 2,500 feet east, where it appears to end in a small gulch or flat. The vein lies entirely within an area of volcanic rocks, consisting of beds of rhyolite tuff with some quartz latite and andesite. On the hilltop and very near the vein reddish rhyolite and quartz latite predominate, but near the present workings on the hillside andesite is the predominant rock and forms the walls of the vein.

The strike of the vein varies from N. 80° E. to due east, and the dip is 70 to 80° south. The vein is of the fissure type and of very irregular width vertically and horizontally. In places its maximum width is about 25 feet, but in the main working the average is about 6 or 8 feet. There are numerous branches, offshoots of the main vein, in the upper workings. On the north side of the hill, paralleling the vein, numerous fluorspar bowlders covered with wash have been found. At the extreme east end of the property the vein has the same strike and dip and near the point where it disappears is about 2 to 212 feet wide. The vein filling is fluorspar, barite, fragments of country rock, and gouge in varying proportions. The wall

25 Aurand, H. A., Fluorspar deposits of Colorado: Colorado Geol. Survey Bull. 18, 1920, 94 pp.

rock is much altered, leaving the walls weak and necessitating extensive timbering.

Development. The mine is developed by an open cut on the outcrop near the apex of the hill. About 150 feet vertically below this point a drift has been driven on the vein for about 1,300 feet. The average width of the ore in this drift is about 10 feet. At the face the tunnel is in a mixture of clay and gravel fluorspar, the latter amounting to about 40 per cent. About 150 feet vertically below this end and 450 to 500 feet above the valley of Goose Creek to the west a tunnel was started in the country rock north of the outcrop, and was driven at an angle intersecting the vein 700 to 800 feet from its portal, then continued into the hill on the vein about 1,100 feet farther. This level was connected with the level above by a raise several hundred feet east of the point where the tunnel intersected the vein.

The vein is of very irregular width, varying from 10 inches to 25 feet and averaging about 8 feet. The vein in the face of this drift is about 12 feet wide and the filling is about 50 per cent fluorspar mixed with andesite breccia and soft gouge. The fluorspar in this mine varies from gravel to large solid blocks of massive spar. At places the vein filling was practically all fluorspar, sometimes a body was 25 feet wide. Practically all of the spar is nearly white, and it is difficult to distinguish barite from fluorspar in the mine.

A tunnel has also been started in the country rock north of the vein about 100 feet above the creek level and level with the top of the ore bin of the mill, and has been driven about 700 feet at an angle so that if continued on its present course it would intersect the vein about 1,000 feet from its portal. The present intention is not to cut the vein with this tunnel, but to parallel the vein about 25 feet north of it and remove the ore through crosscuts driven from the tunnel to the vein. About 40 feet below an old drift was driven on the vein for 400 to 600 feet, but it has caved and could not be entered. Mining. The method now in use for extracting the ore between levels is somewhat as follows: A section of ground 100 to 200 feet long is blocked out by raises at each end, generally to the level above. These end raises are then used for manways and timber is handled through them. The drifts are heavily timbered by drift sets, sometimes aided by cribs filled with waste to help carry the weight of the ore above. Chutes are installed back of the drift at about 25-foot centers and the space between the chutes tightly lagged. Back stopes are then put up for about 25 feet; here heavy stulls are placed from wall to wall and are lagged over, except at intervals where openings are left through which the ore from above (which usually caves badly) is drawn. Grizzlies with 6-inch openings are set here;

the fines pass and the bowlders are sledged through. The ore is then drawn through the lower chutes into 1-ton steel cars in the drifts, horse-trammed to the surface, and dumped into a chute leading to a sorting platform above a large ore bin holding 300 to 350 tons near the portal of the tunnel. The ore is trammed from this bin by a gravity aerial tramway about 1,500 feet down the hill to the mill. Figure 26 shows the bins at the upper end of the aerial tramway and indicates the topography.

As the walls are weak and the ore friable, large amounts of timber are used. Good quality spruce timber is plentiful, and a mill at the

FIGURE 26.-Trestle, ore bins, and waste dump at main tunnel, American Fluorspar Mining Co., Wagon Wheel Gap, Colo.

foot of the mountain saws and frames timbers. An aerial tram from this sawmill to the upper tunnel is used only to convey timbers to the mine. In the early stages of underground mining square-sets were used in the stopes, but an effort is now being made to minimize the use of timber by the mining method described above.

Stopers and jack hammers are used for drilling, the air being supplied by a two-stage, steam-driven air compressor with a capacity of about 900 cubic feet per minute.

Transportation.-Concentrates from the mill are loaded into steel cars holding about 1,500 pounds each and hauled by horses in 12-car trains to the railroad, about 114 miles, where the cars are unloaded into standard-gauge railroad cars. Coal and other supplies are hauled on the return trip.

Future possibilities.-The working of this mine has been well planned and executed. As the walls of the vein are weak and irregular and the vein filling is treacherous, the present system of mining probably could not be improved upon. One cave, about 200 feet long, of vein material from the surface now extends to the lower workings. The caved ore, however, is being handled successfully and probably most of it can be recovered. It is only reasonable to assume that similar caves will occur on the vein. As the walls near the surface are weak and apt to slough into the vein, some ore may be lost. The timbering cost is high and must continue to increase. The character of the ore body apparently has not changed greatly with depth, although the vein is narrower in the lower than in the upper workings.

NORTH GATE

North Gate claims. This property of the Colorado Fluorspar Corporation is in Jackson County, Colo., one-half mile northeast of King's ranch, 3 miles northwest of North Gate station on the Colorado, Wyoming & Eastern Railway. It is in the foothills of Medicine Bow Range near the northern edge of North Park and in the Medicine Bow Forest Reserve. The nearest post office is Cowdrey, 3.7 miles south of North Gate. North Gate is 80 miles southeast of Laramie, Wyo., the junction of the Colorado, Wyoming & Eastern Railway and the Union Pacific Railroad. The property consists of 7 claims; 4 are end to end and traverse the vein as the outcrop indicates, while the other 3 are near the first 4. In addition there is a tunnel site.

Prospectors for copper discovered the outcrop of the vein in 1900, but it was not identified as fluorspar until 1915, when claims were located by a prospector who later interested the present owners. A definite development system has been laid out.

Ore deposit. The deposit extends along the side of a long, low hill which rises 400 to 500 feet above the valley floor at the railroad. The elevation at King's ranch is 8,032 feet, 50 to 75 feet above the railroad at North Gate. The hill in which the deposit occurs consists principally of rather coarse-grained pink granite intruded by numerous igneous dikes. Large pieces of feldspar and quartz show that pegmatite is present. Hard, glassy vein quartz was noted about 100 feet west of the main fluorspar vein.

The strike of the vein is approximately north and south and the dip practically vertical. The south end is about one-half mile west of the nearest point on the railroad, but across Pinkham Creek Canyon. The width of the deposit has not been accurately determined because identification of the walls is difficult due to alteration of the

granite. The outcrop could be traced from its extreme southern point along the side of the hill north to the main shaft and beyond, a distance of perhaps 2,000 feet, but snow covered the outcrop farther north, making examination impossible. The outcrop was said to have been traced for a total distance of about 4,500 feet. No limestone was found in this locality either in place or in wash, therefore the fluorspar was not formed by limestone replacement and its quantity is limited to the fissure filling. At the extreme south end of the visible outcrop the vein seems to be terminated by a fault, whose presence is substantiated by Government maps showing a large east and west fault at about this point and other faults near by. These maps also show limestone formations cut by faults in this vicinity.

Development. The property is opened by two shafts and several open cuts and pits on the outcrop. A prospect shaft 4 by 6 feet has been sunk about 20 feet deep 1,200 to 1,500 feet north of the extreme end of the outcrop. No crosscutting or additional work was done at this point. Apparently the shaft was sunk on the easterly edge of the deposit, and the full width of the deposit has not been mined at this point, as the vein outcrops strongly a few feet west of the shaft. Although the work done here was limited, the ore in sight seemed of the same general character and quality as that at similar depths in the more extensive workings described later.

About 700 feet north of the prospect shaft just noted and 75 to 100 feet above its collar an open cut about 40 feet long, 8 to 10 feet wide, and with a face about 10 feet high at its north end was made on the deposit. This cut shows fluorspar throughout its face and sides in more or less vertical fractures in the granite, which is highly altered here. Fluorspar appeared to constitute about 30 per cent of the vein material; it was solid and crystalline, contained no apparent barite or calcite and but little intergrown silica, and occurred in stringers 6 to 18 inches wide in the altered and fissured granite. Neither foot nor hanging wall of the deposit was in evidence, nor was there any evidence of movement or displacement.

At the highest point on the outcrop-about 25 feet above the level of the cut just described and 50 to 75 feet north of it-a 4 by 7 foot shaft was sunk on the vein 70 feet deep. At the bottom of this shaft a crosscut was driven about an equal distance east and west, with a total length of about 20 feet. The fluorspar occurred here also in practically vertical but irregular fractures in the granite. The fluorspar filling in these fractures is 3 to 18 inches wide. Other fractures in the granite were filled with a granite breccia, fluorspar bowlders, and quartz bowlders embedded in highly