Page 164 - The Geology and Ore Deposits of Sierra County, New Mexico - Bulletin 10

162 GEOLOGY AND ORE DEPOSITS OF SIERRA CO., N. M.
feet at the time of the writer's visit, was later driven to 420 feet from the shaft. According to reports issued by the company, it cut at 35 feet a porphyry dike about 12 feet wide that is said to be low-grade ore ; at 80 feet a sulfide stringer ; and at 140 feet a fault zone said to be 8 to 9 feet wide, which has been drifted on for a few feet to the northeast and also to the southwest. From the face of the northeast drift a sample is reported to have assayed $29 per ton, although the width over which this sample was taken was not stated. This fault zone is believed to be the El Oro vein. At 232 feet from the shaft another porphyry dike, which is apparently over 20 feet wide, was encountered, and this is also designated as low-grade ore. At 276 feet from the shaft it is stated that a mineralized zone 45 feet wide was penetrated, and that 18 assays taken in this distance give an arithmetical average of $8.84. At 340 feet an oxidized vein 2 to 3 feet wide is reported, and at 350 feet a vein is said to have been cut that is 10 to 12 feet in width and oxidized, but no assays of these veins were given. At the face of the tunnel it is reported that a sulfide vein containing very rich ore was encountered, but the width and assay returns of this material are not stated. This sulfide vein is located at a point within 5 feet of where the writer's projection of the vein in the saddle on the ridge back of the plant would place it.
At the time of the writer's last visit (Oct. 1, 1933) the new El Oro shaft was the main hoisting shaft. It was equipped with concrete collar, a steel headframe, coarse-crushing plant, belt conveyor and mill. The steel-frame and corrugated-iron power and hoist house was equipped with a hoist, one 350-H.P. Worth- ington Diesel engine, one 450-H.P. engine of similar make and design, two compressors of 650 cubic feet capacity each, and a complete switchboard. Each engine is direct-connected to an electric generator. The mill was a steel-frame and corrugated- iron building equipped with fine-grinding mills, classifiers, flotation machines and filters, with a rated capacity of 300 tons per day. There is considerable doubt in the writer's mind as to whether an adequate water supply is economically available to keep a 300-ton mill in operation on even a part-time basis in this district. It was understood that the surface plant on this property, as described above, was being built under a contract agreement with an Arizona firm of metallurgical and construc- tion engineers for $150,000, and that with all incidental expenses included, the plant would cost between $175,000 and $200,000. Most of the equipment furnished for this construction was sec- ond-hand material, but all said to be in excellent condition.
One of the company officials stated that the new shaft would be put down another 1,000 feet, or until the contact between the andesite, and underlying limestone or monzonite porphyry was cut, in the hope of finding new ore bodies at a greater depth than any discovered heretofore. It was also proposed to continue