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Mexico Operations

Mexican Mining Operations

Although USAC has extensive antimony mineralization at Thompson Falls, Montana, the time and cost of re-permitting the mine as well as the uncertainty of even getting a permit caused USAC to return to Mexico to mine. Most of the Mexican antimony deposits are oxide ores or mixed oxide sulfide deposits. The oxides are recoverable by gravimetric methods, typically jigs and tables. The sulfide ores are recoverable by flotation. During World War II, the United States relied on Mexico for antimony for military applications. Historically, Mexico was at one point the second largest producer of antimony in the world. USAC does not claim any reserves by S.E.C. definitions.


At the Los Juarez property USAC relied on a Mexican Government publication, Consejo de Recursos Minerales, Monografia Geologico-Minera del Estado de Querearo, pages 74-75. The paper reported a reserve of 1,000,000 metric tons containing 253 grams per ton silver and 1.8% antimony 40 hectares (100 acres). The deposit was interpreted as a manto (layered) deposit up to 5 meters thick. Although USAC used the report to start mining, it was disallowed by the S.E.C. as a basis for reserves. Detailed mapping and sampling delineated jasperoid mineralization over an east-west strike length of 3.5 kilometers with a maximum width of 1 kilometer. Unlike most Mexican deposits, this deposit is primarily all sulfide. Preliminary exploration indicates that it could be a deep-seated jasperoid. USAC controls this property directly. The grade of 1,415 tons of rock from the Minas Grande area that was milled assayed 0.728% antimony, 6.22 ounces (193 grams) of silver per metric ton, and 0.023 ounces of gold (0.7 grams) per metric ton.


USAC is sourcing mill feed and DSO for Madero from the Soyatal District in the State of Queretaro, Mexico. The deposit was the third largest antimony producer in Mexico. Donald E. White (U. S. Geological Survey Bulletin 960-B, Antimony Deposits of Soyatal District, State of Queretaro, Mexico, 1948) prepared an extensive report and said that the production (p. 40) was estimated through 1943 at 25,630 metric tons of metal contained. USAC has purchased this property but claims no reserves.


According to the U. S. Geological Survey (Bulletin 946-E, San Jose Antimony Mines Near Wadley, State of San Luis Potosi, Mexico, 1946, Donald E. White and Jenaro Gonzales R.) by 1943 the “San Jose mines have produced more antimony than any other district in Mexico, and they have been surpassed in production by only one or two other deposits in the world.” By 1943, the recorded production was 57,612 metric tons of contained antimony metal. Since that time the mine has probably produced another 25,000 metric tons of metal. Although the Rotterdam price of metal peaked at $17,879.00 per metric ton during April 2011, 2013 prices averaged $10, 418 per metric ton. The mineralization is primarily is in five layered deposits or “mantos” that were fed by fracture filling veins that also contain mineralization. The zone is approximately 2 kilometers long and a kilometer in width and has been developed by 500 kilometers of drifts and tunnels. There are more than 500 kilometers of drifts and tunnels. The ore consists almost entirely of oxide minerals that were recovered by hand-sorting “direct shipping ore” for smelting. Gravimetric concentration of the lower-grade material did not start until a water well was drilled. In 1943, the U. S. Geological Survey noted “If the mining of low-grade ore becomes feasible in the future, large tonnages can be blocked out in the mantos and in the veins. In addition dumps resulting from more than 50 years of mining are readily available… The future of the San Jose mines depends to a large extent upon the development of a milling process by means of which antimony can be extracted from low-grade oxide ores…The mines have been operated for the high-grade deposits — those that contain ore that can be sorted to an antimony content of at least 30 percent.” In the late 1990’s a heavy media separator (HMS) plant was installed with a capacity of up to 500 tons per day. Unfortunately, the plant recovered only 20-25% of the values and made a low-grade concentrate. USAC claims no reserves at the present time at Wadley. In the last two years, USAC produced __pounds of contained antimony from Wadley direct shipping ore (DSO) sent to the USAC smelter at Madero, Mexico.. The DSO was mined by a prior operator. During this time USAC utilized the crushing and screening circuit of the HMS plant and added gravimetric equipment to produce a 40-50% antimony concentrate with up to a 55% recovery. The main headquarters at Wadley include a man-camp, assay lab, hospital, administrative offices, store, railroad siding, shop, warehouse, mess hall, gardens, entertainment area, guard house, equipment and parts.

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