OSCEOLA MINE 1900-1925
The Osceola mine is on the west bank of the North Fork of Kanaka Creek, just north of Alleghany. The property includes the Osceola (patented) and Osceola Fraction claims. The owner in 1925 was R. W. Gillespie.
The mine has been operated intermittently since the early days of the district, and the total production is uncertain. Local reports give information of a shoot in the middle tunnel that yielded $30,000 and one in the lower tunnel that yielded $60,000. This must have been prior to 1895. The mine was reopened between 1900 and 1902, and about $12,000 was produced. It was again reopened in 1913, and a small amount of development work done, probably without notable production.
There are three tunnels on the vein. The uppermost, a short distance beneath the lava, has 120 feet of drifts, with two raises and a winze. The middle tunnel is caved 30 feet from the portal. This is said to have been the most productive and to contain extensive stopes. The lowest or main tunnel close to the North Fork of Kanaka Creek has a total length of 1,550 feet but is now caved 200 feet from the portal. In the portion now accessible the ground is partly stoped above the tunnel level and stoped in places below. Near the portal is a winze said to be 150 feet deep, now flooded. As the total extent of the workings is unknown, the ratio of production to development can not be given closely.
The country rock is amphibolite schist of the Tightner formation, showing the usual variation in texture and in places heavily silicified. The amphibolite is cut by narrow serpentine and gabbro dikes, in places without sharp contacts.
The displacement of the serpentine on the surface and in the middle tunnel indicates that the vein follows a fault of small normal throw. In the lower tunnel the relations are confused by the splitting of the vein and the presence in the hanging wall of dikes of gabbro and serpentine which were not found on the footwall side. In the productive portion, close to the serpentine, there has also been minor postmineral thrusting nearly along the plane of the vein.
The vein has a very prominent outcrop on the hill west of the creek just below the lava and is easily traceable on the surface as far as the creek. East of the serpentine belt the vein splits, and the two branches have also been developed on the tunnel level. The footwall branch continues to the southeast and is probably the same fissure as that followed by the Colorado vein on the ridge between the forks of the creek. South of the creek what may be the same vein has been developed as the Bullion vein of the Eldorado mine and is traceable uphill to the south at least as far as the 4,100-foot contour, in all a distance of about 4,500 feet. The hanging-wall branch becomes indefinite at its contact with serpentine in the creek bed, but the small Panama vein, 500 feet to the southeast, may be on the same fissure.
The tunnel was visited by Mr. Gannett in the early part of the field season of 1925, before the last cave occurred, but was not studied in detail. His preliminary notes indicate rather less continuity of quartz filling than on the same vein in the Yellow Jacket workings, to the southwest. Minor postmineral faulting nearly parallel to the plane of the vein has in places caused gouge streaks to cross the vein from footwall to hanging wall. The strike of the grooving on these streaks where recorded is N. 60° E.
For the first 400 feet from the portal the vein has an average strike of N. 42° W. and a dip of 55°-60° NE. Beyond this point the sketch map shows an average strike of N. 60° W. and dip of 75°-80° NW. There are stringers in the hanging wall following the strike of the southern segment of the vein. It is possible, therefore, that this change in strike may represent another split in the vein (in the opposite direction from that near the portal) and that an unexplored segment lies to the north. Notes made in 1913 by H. G. Ferguson, when the full length of the tunnel was open, indicate that near the face the strike is N. 25° W. and the dip 35° E. This may indicate a bending toward the Sixteen to One fissure similar to that of the Ophir vein. Quartz is entirely lacking between points about 700 and 1,150 feet from the portal, but thence to the face it is continuous.
The known high-grade stopes are near the junction of the two branches near the portal of the main tunnel and also close to the small serpentine dike cut by the vein. So far as known no high-grade shoots were associated with changes in dip and strike of the vein. Mariposite is abundant only near the serpentine. In part at least the gold occurred in association with crushed arsenopyrite.
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