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By R. H. Waesche, Ranger Naturalist A NUMBER OF COPPER deposits have been discovered in the vicinity of the Grand Canyon. Several of these are located below the rim, others are found on the surfaces of the Kaibab and Coconino plateaus. Mining operations on a small scale have been attempted at not less than five different localities. Much of the copper ore of Grand Canyon -- including that discussed in this article -- occurs in the Kaibab limestone of Permian Age which composes the surfaces of the plateaus. This is the same formation seen as the topmost stratum in the Grand Canyon. It is a comparatively sandy limestone about five hundred and fifty feet thick. The Kaibab as well as the other Paleozoic sediments in the Grand Canyon are nearly flat-lying, showing only rarely indications of dynamic disturbance. Evidence of such disturbance is seen in the existence of several faults which cut across the plateau in a north-south direction. Besides the faulting, there has been slight folding in some places as may be readily seen at Grand View. It is quite likely that both the faulting and folding have a direct bearing on the origin of the copper ores. The ore minerals are almost exclusively the carbonates, azurite and malachite. Some sulfide, chalcopyrite, has been noted by E. P. Jennings* in the plateau copper deposits. Associated with the copper carbonates is brown limonite which colors most of the rock not stained by the blue and green copper. Dendrites of manganese oxide are plentiful. Traces of gold are said to be present in siliceous materials. The ore minerals are found disseminated in the limestone and in a sandy phase of the same horizon, thus they are of two types, calcareous and siliceous.
One of the most accessible and interesting deposits of copper in the Grand Canyon area is at the Anita mine, near Anita, Arizona. This place is a water station on the Santa Fe railroad, about fifteen miles south of Grand Canyon. The mine is located about two miles from the station, on the south rim of a small canyon through which winds the old highway to Grand Canyon.
The Kaibab limestone in the vicinity of Anita is very much brecciated but no definite fault has been observed. The brecciation occurs in a zone running northeast-southwest, an undetermined distance, probably not great, and having a width of several hundred feet with concentration of ore minerals greatest near the center of the zone. Other zones are said to parallel this one in the sane region. It is likely that the disturbance here is related to the faulting and folding of the plateau previously mentioned. The sandy, brecciated material, southwest of the lime area, contains definite sand grains and rounded pebbles which may indicate a previously existing stream bed. There is room for speculation as to just what the source of these pebbles may have been. It seems quite likely that the copper may have gained access to the Kaibab limestone along the channels created by the jointing and brecciation of the sediments. The copper-bearing solutions have replaced the more soluble parts of the limestone, leaving small lenses and stringers of carbonate ore. The ore is richest along these fracture lines. Certain beds seem to have been affected more than others and in some cases the replacement has followed bedding planes. According to the owner, Mr. Lockridge, the mineralization extends to a depth of one hundred and sixty feet below the surface. The source of this ore is doubtful. It is hardly possible that it could have been derived directly from igneous materials. The pro-Cambrian granite intrusion of the Vishnu schist and the forming of diabase sills in the Algonkian rocks occurred long before the Paleozoic sediments were deposited and no later igneous activity is known in the immediate vicinity. The minerals themselves indicate that the ore is not related to igneous activity. No gangue minerals such as fluorite, tourmaline, or apatite, which are commonly associated with ores of igneous origin, have been observed. Chalcopyrite is the only sulfide found and since it is often present in rocks net associated with igneous activity, it indicates nothing. No arsenic or antimony compounds are found, suggesting further that the ores are not of magmatic origin. Chalcopyrite, which is found in surface deposits of the plateau, may have been derived from oxidized sulfate solutions brought down from overlying strata or it may have been derived from concentration of copper present in the Kaibab itself. It is possible that chalcopyrite was the original copper mineral present and was later oxidized to form the existing ores. The distribution of the replacements suggest that they were deposited in the limestone by descending meteoric waters. The veins of copper follow brecciation zones which are vertical or steeply inclined above but which branch and assume a more horizontal position as they descend. The idea of deposition by descending waters is supported by the fact that Triassic sediments present to the north of the Grand Canyon and which at one time extended over the Kaibab are known to be copper-bearing*. From this it would seem that at some time after the Triassic sediments had been deposited above the Kaibab, the region was subjected to deformation resulting in the dome shape of the plateau as well as the faulting and folding evidenced. The fracture zones which resulted from this disturbance could have offered easy access to meteoric waters carrying the copper from the Triassic sandstones to the Paleozoic strata below.
The Anita copper deposit was discovered by Bucky O'Neill, one of the earlier settlers of the Grand Canyon region. The exact date of discovery is unknown but the property was in the possession of a Mr. Nellis in 1890. Mr. Nellis was a pioneer in the town of Williams. The property then passed into the hands of William Nesmith of New York and in 1912 the present owner, Mr. W. H. Lookridge of Anita, came into possession. The Anita mine is a small one consisting only of one level, the main part of which is a tunnel driven south about eight hundred feet from the edge of the small canyon on the rim of which the operation is located. Little or no development work has been done. Apparently the ore was removed as discovered. Several very short crosscuts have been driven at intervals along the main drift. The surface is honeycombed by holes sunk to the various crosscuts and to the main tunnel. A timbered shaft, six feet square and thirty-five feet deep, has been sunk to the working level about four hundred feet south of the tunnel entrance. This shaft is the deepest hole associated with the workings. The ore was brought to the surface in a bucket by a hand-operated hoist. At a number of places not supported by props, the brecciated material of the unsound roof has caved, partially filling the tunnel and crosscuts. In the early history of the mine a smelter was constructed at Williams to handle the ore but this was never operated. The ore was hauled in a small car from the face of the workings to the original tunnel opening. The tracks for this car have since been pulled up and removed from the mine. After being brought to the surface the ore was placed in a series of trailers, attached to a tractor, and hauled to Williams, Arizona. The tractor was powered with steam generated by a wood fire. Wood was piled at intervals along the road to Williams for fuel purposes. A railroad spur was later constructed from the Grand Canyon branch of the Santa Fe railroad but was used little or none. All that now remains of the spur is the grade as the rails have been removed. Mining methods were quite simple and on a small scale. Stoping was in evidence, but none of the stopes were greater than twenty feet across or ten feet in height. The ore was shot down with forty per cent dynamite and then removed with pick and shovel. Drilling was done by hand. In recent operations most of the work was done by Mr. Lookridge and his family, employing around two or three people altogether. The material was removed from the face to the shaft in wheelbarrows and from there, after being sorted by hand, it was transferred to trucks and hauled to the railroad spur at Anita. Ore has also been shipped to smelters at El Paso, Texas, and to Hayden, Arizona. At times it was hauled by truck two hundred miles to Kingman, Arizona. The last shipment was made three years ago, to Hayden. In 1914 Mr. Lookridge had a contract for thirty tons of ore per day. The mine was operated to this extent for ninety days, during which time fifteen to twenty men were employed. This is the most extensive work done at any time. At no time has the mine been what would be called a paying proposition and, as is usual with such ventures, law suits have been common. In a recent suit the present owner obtained $2100.00 for thirty tons of ore. He has also won several first prizes at the Northern Arizona State Fair for his exhibition of copper minerals.
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14-Oct-2011
