The first discovery on the area covered by the Nieves Property was the Santa Rita Vein in 1560 by Spanish explorers (Turner, 1999; Cavey, 1999). Soon after, in 1574, the Concordia vein was discovered. The Santa Rita and Concordia-San Gregorio-Dolores veins were the focus of mining by the Spanish and Mexican miners until 1880.
Concordia Legacy Shaft
San Gregorio Legacy Shaft
Delores Legacy Shaft
Most of the mining activity in the Nieves District occurred between 1880 and 1910, when an English company, the Mexican Rosario Mining Company, and two Californian companies, the Almaden Mining Company and the Concordia M. and M. Company, worked in the area. These companies worked on the Concordia vein primarily while a small independent miner, Gonzáles Piñera, worked concurrently on the San Gregorio vein (Turner, 1999; Cavey, 1999). The location of the old mines are shown in Figure A.
Prior to the 1910 revolution which halted all production in the Nieves District, total ore production in the District was estimated at 50,000 metric tons (tonnes) (Turner, 1999). The only production reported is from the Concordia Mine where 5,414 tonnes at a grade of 4,065 g/t silver were produced. This production data cannot be relied upon and has not been verified by the qualified person. The qualified person has not done sufficient work to classify the historical production as current mineral resource and is not treating the historical estimate as current mineral resource.
Refining and smelting stuctures (Spanish)
Between 1910 and 1978, several companies (including Fresnillo Mining: 1936; Scurry-Rainbow: mid-1960’s to 1978) attempted to de-water, sample, and re-open the historical workings in the Concordia and Santa Rita mines, and were largely unsuccessful. However, underground drilling from this period intersected and confirmed the presence of the Santa Rita Vein 100 m below the 8th level. Included in this time period, is a site visit by D.B. Dill for Peñoles Mining, in 1954, who compiled and preserved much of the historical data for the Nieves District. Dill (1954) reported 21,500 tonnes of probable ore at a width of 0.92 m and a grade of 0.92 g/t Au, 1131 g/t Ag, and 2-4% Sb, still remained in the Concordia Vein and a prospective 120,000 additional tonnes. This resource estimate cannot be relied upon, has not been verified by the qualified person, nor is it a NI43-101 compliant resource estimate. The qualified person has not done sufficient work to classify the historical estimate as current mineral resource and is not treating the historical estimate as current mineral resource.
The Santa Rita vein and refurbished mill and flotation plant were purchased by Fomento Minero in 1978, who operated the mine until 1987. Fomento Minero also sank three shafts and deepened a historic shaft along the Concordia- San Gregorio vein system during the 1970’s. The flotation mill was capable of running 100 tonnes/day during this time and was fed 50% tailings and 50% ore with an average head grade of 130 g/t silver, 2% lead, 2.4% zinc and 2.5% antimony, according to Consejo Recursos Minerales (CRM) (Cavey, 1999). Today, all that remains are the building foundations, abandoned shafts and power lines.
13 Known Legacy Shaft Mines