Iron Ore Areas In 1956, Utah Construction & Mining Co. undertook a field investigation of 20 iron ore areas in western Mexico to determine the nature of mineralization, potential reserves, and competitive capability relative to Peru. Most of this work was performed by Mexican consulting geologists and required several months to complete. One major deposit, Pena Colorado, was drilled in the fall of 1956 on a contract basis for Colorado Fuel and Iron Company. The Pena Colorado ground has since been nationalized and is scheduled to be brought into production in 1972. With only three exceptions, Mexican iron ore deposits are relatively small and occur as roughly lenticular bodies of hematite, magnetite and accessory sulphide, and silicate minerals. The iron mineralization is localized at or near contacts of Tertiary intrusive igneous rocks with intruded calcareous sediments or volcanic rock or both. The largest known deposit Las Truchas averages 57 to 62 percent Fe, 2.5 percent sulfur, and 0.7 percent phosphate. The gangue minerals are garnet, epidote, and pyrite. The potential for developing additional iron ore of the contact metamorphic type is good, particularly in the coastal states of Oaxoca, Guerrero, Michoacan, and Sinaloa. Reportedly, there are large areas concealed by volcanic or alluvial cover that are amenable to prospecting with airborne magnetometers in combination with photogeologic mapping. 41