Hall Molybdenum Mine (Hall's Mine; Anaconda Mine; Liberty Mine; Cyprus Tonopah Mine; Tonopah Copper Mine), San Antone Mining District, San Antonio Mountains, Nye County, Nevada, USAi

Regional Level Types
Hall Molybdenum Mine (Hall's Mine; Anaconda Mine; Liberty Mine; Cyprus Tonopah Mine; Tonopah Copper Mine)	Mine
San Antone Mining District	Mining District
San Antonio Mountains	Mountain Range
Nye County	County
Nevada	State
USA	Country

A former Mo-Cu-Ag-Au mine located in secs. 4, 5 & 6, T5N, R42E, and in sec. 32, T6N, R42E, MDM, on the west flank of the San Antonio Mountains, about one mile N of the Liberty Mine, on Bureau of Land Management-administered land (Tonopah BLM district). Discovered 1863. Operated between 1979 and 1991. Production years: 1979-1985, 1986-1991. Owner-Operator Anaconda Copper Co., Tom Parker, Project Manager, Tonopah, NV 89049 (1984); Owned by Cyprus Amax Minerals Co. (100.00%), Colorado (1996 1988); Owned by owner-operator Equatorial Mining North America, Inc. (2004). Operated by Cyprus Tonopah Mining Corp. 2602069, Nevada (1996 198)8. MRDS database accuracy for this location is not stated.

Mineralization is a porphyry Cu-Mo deposit (Deposit Model code 80; USGS model code 21b; deposit model name: Porphyry Mo, low-F) hosted in quartzite and schist. Alteration types affecting host rocks are sericitization, kaolinization, silicification. The ore body is oxidized to about 150 feet in depth.

Local geologic structures include a sheared contact zone.

There are several ore bodies. The ore bodies's general form is as small flakes, bunches, and thin coatings. The depth to bottom is 77.42 meters, width is 15.24 meters, length is 365.76 meters, striking N45E and dipping 15E, at 40 meters thick and a depth to top of 3 meters. A second ore body is 760 meters wide and 760 meters long. They are replacement bodies. Primary mode of origin was hydrothermal. The secondary mode was oxidation. Primary ore control was the contact zone along a strongly sheared contact zone between schist and quartz monzonite porphyry and secondary control was igneous. There is moderate wall rock alteration (potassic, silicification & other).

From the Anaconda Nevada Moly record: General size of ore body - large. Ore also controlled by faulting. Dip of mineralized zone ranges from 15-50 degrees East. The deposit is located within a large, well-defined quartz monzonite intrusive rock. The ore body is pipe-like; the West side is cut by a normal fault and down dropped to the West. The deposit is divided into three zones; upper, middle, and lower. The upper zones are exposed in the West and central portions, and covered in the East by a series of volcanics. The upper zone is almost entirely exposed and ranges in depth from zero meters on the West to 240 meters on the East. It is an oxidized zone made up of copper minerals in quartz monzonite, and constitutes the copper ore body. The upper zone must be stripped to mine the molybdenum ore body. The amount of supergene enrichment is inconsequential. The relative proportions of the various mineral components must remain conjectural. The middle zone lies immediately below the upper zone, is approximately 150 meters thick, and rakes to the East at 15 degrees. It is unoxidized and is composed of chalcocite and molybdenite in quartz monzonite. The middle zone constitutes the main molybdenum ore body. The lower zone is separated from the middle zone by 120 meters of barren rock. It is approximately 90 meters thick and is made up of molybdenite in quartz monzonite. Creedite is also present.

From the Anaconda Nevada Moly record: Quartz monzonite is really a quartz porphyry. Unspecified metamorphic is really metamorphosed sediments.

Anaconda Nevada Moly record: Alternate name - Hall Copper. Formerly listed as Seq# 0320230159. Company says deposit has estimated minimum reserves of 150 million short tons and expects to extract 6,000 short tons per year Mo over 20 years. Also called Hall Molybdenum. Cyprus Minerals Company planned to obtain approval to acquire control of the Tonopah Mine, M-J /29/88. Purchase is complete per J. Blossom 8/29/88. Per 9/88 Paydirt, Tonopah could produce 2-3 MM pounds Mo in 4th quarter, 1988. Mine in care & maintenance STATUS AS OF 1991.

From the Anaconda Nevada Moly record - Eighty percent of resource is in the quartz porphyry intrusive.

Associated rocks include quartz monzonite and alkali-granite (Alaskite). Local rocks include Quaternary alluvial deposits.

Workings included surface and underground operations. The underground workings had a length of 1,356.36 meters. Workings consist of a 310-foot 65 degree inclined shaft, a 180-foot vertical shaft, a 150-foot vertical shaft and an open pit more than a half mile in diameter. Plant type was beneficiation (mill); milling method was flotation.

Reserves in-situ were estimated in 1983 to total 455,000,000 metric tons of ore. Mo at 0.072000 weight % and Cu at 0.060000 wt-%.

The molybdenum orebody as delineated in the 1940s on the 280 foot level contained 1.3 million tons of developed and indicated ore averaging 0.37 % molybdenum sulfide. Anaconda's patent application report in 1970 contains an estimate of 123 million tons of proven ore with an average grade of 0.126 % molybdenum sulfide and 0.1 % copper. Equatorial's drilling and geologic evaluation completed through 1999 resulted in a proven ore reserve of 98 million tons at 0.343% total copper. The total copper resource was estimated at 137.8 million tons averaging 0.314% total copper. The total amount of copper and molybdenum production from the deposit is unknown. Hall is considered by the USGS to be one of the ?Giant Porphyry-Related Metal Camps of the World?

The area near Liberty Springs, a mile south of the Hall mine area, was the site of sporadic silver mining from 1876 to around 1900, producing about 100,000 ounces of silver. Clarence Hall developed an underground silver mine on the property that later became the Hall deposit. It was explored by U.S. Vanadium Corp in 1935-38, by the USBM in 1942, and by the Metals Reserve Corp. (Desert Silver Inc.) in 1943. During World War II, the Hall deposit was identified as a molybdenum resource with 354 feet of diamond drilling completed on the property by 1945. Anaconda Company procured the deposit in 1956 and outlined the molybdenum orebody in the 1970s. Anaconda applied for patent on 19 of the key claims of the property in 1969 and was granted patents on 18 of the claims in 1970. Economic feasibility studies were done in 1978, production started in 1979 and lasted through 1985. In 1981, over 1000 persons were employed in development and construction at the site. The property was listed as an active open pit mine and mill, flotation, tank leach operation in 1983, employing a total of 306 persons. Subsequently the property was sold to Cyprus Metals who reopened the mine in 1986 and operated it through 1991. Equatorial Mining North America, Inc. acquired property adjacent to the site of the former Hall Molybdenum Mine in 1997 and in 1999 opened it as an open pit heap-leach copper mine. Equatorial's copper operation closed in 2001 and is undergoing reclamation. Efforts are currently (2004) being made to use some of the facilities at the site for renewable energy production (solar and wind).

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Link to USGS MRDS:	10310364

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References