| Description |
In 1928, Utah Construction Company completed its first project outside of the United States with the 110 mile railroad for Southern Pacific of Mexico. Over the next 30 years, UCC continued to work on projects in Mexico including dams, roads, mining, and canals. The collection contains several booklets and correspondence along with approximately 500 photographs. |
| OCR Text |
Show Most of the production is from relatively shallow underground mines worked by shrinkage, cut and fill, or room and pillar mining methods. The terrain is generally rugged and transportation poses serious problems because of mountain dirt roads, a four- to five-month rainy season, and washouts and floods. In the Parral District of Chihuahua, mill tailings resulting from the old underground zinc, lead, and silver mines are currently being reworked to recover fluorspar in a flotation mill. It is estimated that 45 million tons of tailings contain about 5 million tons of recover-able acid grade concentrate. Tin There are probably more than 1,000 tin deposits most of them small veins but some of them placers in the volcanic rocks on the plateau of Mexico, principally in the states of Durango, Zacatecas, and Guanajuato. All of these deposits are very similar in mineral composition. They are also distinctly different from the hydrothermal tin deposits of Southeast Asia and Bolivia. Most of the Mexican deposits are in late Tertiary rhyolite, but a few are in latite and andesite that underly the rhyolite. They exhibit a marked simi-larity to the Black Range tin deposits in New Mexico and Lander County, Nevada, with veinlets consisting largely of specularite that is intimately associated with cassiterite. Under the mining conditions and tin prices prevailing today, the production of cassiterite from veins and placers derived from volcanics in Mexico is not likely to exceed 400 tons per year. Even at a price of $2.00 per pound for tin, production would probably not exceed 1,000 tons per year. During the critical tin shortage of World War II, a con-certed effort was made to prove up commercial reserves in the United States and Mexico; however, the generally low grade of the tin caused mining to be uneconomic. Minor Metals Mexico is also a producer of four minor metals graphite, antimony, mercury and barite (see Table 9) that have received some attention. Manganese might also be mentioned, although production of this metal is of no economic significance in Mexico today. 38 |
