History of Gold Mining in Mexico
The history of gold mining in Mexico is very old. Probably, up to the invasion of Mexico, gold alone was found in America, or if any silver was produced, it must have been in such small quantities. Hernan Cortex arrived to Mexico in 1519, and in his advance towards the capital received 2560 marcs of gold at Chalco; and subsequently 100,000 ducats from Montezuma. The mineral wealth of Mexico consists more of silver than gold, although the latter is very abundant. The gold contained in the silver was never properly separated from it, after the communication between the interior and the capital was closed. None of the departments possessed a Casa del Apartado, in which the chemical process of separating the two metals, when combined, is performed. Although some portion of the gold may have been obtained by the use of quicksilver in the arrastras (crushing mills), whatever remained incorporated with the silver was sacrificed. Part of the amount of gold produced annually before the Revolution passed through the Casa del Apartado.
The mines of Tlalpujana were located upon the slopes of te mountains by which the valley of Tlalpujana is formed. Their position was favorable for drainage by adits; and the shafts were no difficult to access. The metalliferous veins of this district were found mainly in the phyllade, which contains in subordinate strata grauwacke, grauwacke slate, transition limestone, talkschiefer and quartz. The vains of Laborda and Corona varied in dimensions. las Virgines attained in some parts a width of 27 ft and the ores contained native gold (hexahedral gold of Jameson) and native silver (hexahedral silver), which were found in small quantities. Rhomboidal silver-glance was abundant and next to it hexahedral silver glance. The red silver or argent antimonie sulfure rouge was less common.
The gold mine of San Jose del Oro in the mining district of Zimapan was formerly immensely productive. The ore was composed of feldspar and copper, intermixed with gold, which was found in very minute particles, and was separated from copper in a few hours by the use of quicksilver in the arrastras. The mine of El Oro (Rancho del Oro) was located just within the confines of the state of Mexico. In August, 1826, El Rosario wa the only shaft from which the ore was raised. The vein appeared to be rich, but small. The gold was found in particles, imperceptible to the naked eye in a matrix of quartz, which contains silver sulphides disseminated throughout the mass in narrow stripes. Gold mines in Mexico generally diminished in value as they increased in depth.
The mine of Villalpando was located in the mountains to the east of Guanajuato. The deepest level did not exceed 550 ft. San Juan de Rayas is one of the most valuable mines upon the mother vein of Guanajuato. This vein was composed of several parallel veins. Rayas is located in a ravine immediately below the mines of Santa Anita and San Vicente. The extraordinary richness of the ores of Santa Anita, some of which were sold during the great bonanza of that mine in 1740 for their weight in silver, in consequence of the large proportion of gold contained in them, first induced to the owner of San Juan de Rayas to carry out his own works below them, this was ultimately done, and exclusive possession of the vein obtained. The first great bonanza was obtained through the shaft of Santa Rosa.
The mines of the Cerro de San Pedro, near San Luis Potosi were abandoned for many years due to the low grade ore, which notwithstanding of the gold grade were explored. The State of Duarngo is rich in mineral deposits, none of which excepting Guarisamey and San Dimas were extensively worked. The mines were worked as long as the water could be raised without inconvenience by two or three carriers with leathern buckets, and abandoned when the discharge of this duty became too laborious.