Page 163 - The Geology and Ore Deposits of Sierra County, New Mexico - Bulletin 10

MINING DISTRICTS 161
the district has also been purchased. The old camp of Andrews was in this part of the district, and several of the old adobe houses in use at the El Oro camp, including the manager's and superintendent's residences, have survived from that period of the camp's activity.
The property covers the northeastern lobe of the monzonite porphyry cupola that extends along the floor of Copper Flat and for a considerable distance through the upper reaches of Dutch Gulch. This area is in• a zone of shearing that is a continuation of the one noted in the Snake and Bonanza mines and in the mon- zonite porphyry floor in the basin of Copper Flat. The lobe of monzonite porphyry ends at a point a few hundred feet south- west of the El Oro shaft, but a number of latite porphyry dikes continue on down the gulch, and it is along the borders of these dikes and in parallel fractures in the andesite that the veins occur.
The development work consists of a large number of pits, trenches and other shallow workings along the outcrops of the various dikes and fracture zones, from which small shipments of high-grade hand-sorted ore have been made. In addition to theSe shallow workings, several shafts from 75 to 240 feet deep have been sunk on the Golden Rule vein, and from these approxi- mately 1,400 feet of drifting on the vein is said to have been done. Above the 200-foot level all ore is reported to have been stoped from the Golden Rule vein by the early operators. The main shaft of the Golden Rule vein, known as Shaft No. 2 in the reports of the company, is down to the 400-foot level, with slight additional depth for a sump, and from each level drifts have been driven. The total length of these drifts is about 1,700 feet. The longest level to the north from this shaft is the 400- foot level, which is about 430 feet in length, while the longest drift to the south is the 100-foot level, about 230 feet long. This vein, as exposed by the old workings and where it has not been stoped out, is said to average $30 per ton, but it is difficult to accept this figure in view of the average grade of past shipments made from this district.
Southwest of the Golden Rule main shaft and a short dis- tance up the hill from the gulch in which that shaft is located, a new shaft has been sunk by the present owners to a depth of 500 feet in andesite breccia, andesite, and latite porphyry flows. From the bottom level of this shaft a short crosscut has been driven to the northwest, and at about 30 feet from the shaft it en- countered broken andesite carrying stringers of pyrite. At 40 feet from the shaft a latite porhpyry dike was cut, which ap- peared to be dense and barren, and to strike northeast, parallel to the trend of Dutch Gulch. This drift, if extended sufficiently, would cut the Golden Rule vein at a new low level, and at some distance south of the present openings in the vein. A similar crosscut to the southeast, which was open for a distance of 90