Abstract The Naica mining district is located in the municipality of Saucillo in south-central Chihuahua State, 110 km directly southeast of Chihuahua, the state capital, at an altitude of 1,382 m and geographic coordinates 27°52′00″N, 105°26′15″W (Fig. 1). Access to the district is by a 26-km-long paved road joining the Panamerican Highway at Conchos Station and another road, also paved, that runs for 40 km to Ciudad Delicias; the México- Ciudad Juárez Central Railroad stops at Conchos Station. The first mining concession in the district was granted in 1794 (Aldama, 1945). The deposits were discovered by prospectors, and small-scale mining began in 1828, during the rainy seasons only owing to the scarcity of water (Lambert, 1892). In the last years of the nineteenth century the Compañ×;a Minera de Naica, S. A., began industrial operations, which were later (1911) suspended when the mine reached ground-water level, and also because of the country's political instability at the time. In 1924 several companies renewed the extraction of oxidized ores. This work continued until 1951, when the Fresnillo Company acquired the Naica Mine and installed electric pumps and a 400 ton/day sulfide-processing flotation plant (in 1952), which doubled production capacity the following year. In 1956 the Fresnillo Company acquired all the deposits in the district and is presently the only producing company under title of Compañ×;a Fresnillo, S. A. de C. V.; since that date the plant capacity gradually increased to 3,000 tons/day in 1985.

Abstract The majority of Mexico’s carbonate replacement deposits were discovered in outcrop over 100 years ago and most were oxidized to significant depths. Oxidized mantos and chimneys were diligently exploited as continuous compact bodies of silver-rich cerussite and anglesite, while ignoring then-valueless underlying or surrounding irregular, high-grade (>20% Zn) bodies of mixed Fe-Mn-Zn oxides, smithsonite, hemimorphite, willemite, and hydozincite. Recent development of effective solvent-extraction metallurgy to recover zinc from zinc oxide minerals has renewed interest in these bypassed bodies, but in most cases little was recorded of their tonnage, grade, or morphology. However, an understanding of original sulfide orebody limits, composition, morphology, and leaching processes can provide a first-order indicator of the potential zinc content and mineability of a given deposit prior to mounting a full-scale exploration effort.