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San Juan Rayas, Guanajuato, Mexico

 

The mining district of Guanajuato is located to the northeast of Mexico City, in the centre of the state that bears the same name, Guanajuato. The area where the lode of silver is mined, about 20 kilometres long, a location known of since the Spanish settlers arrived. The southern parts of this territory were the empires of the Chichimecas, natives who paid homage to the Aztecs. In 1529, Nuño de Guzmán conquered this region. In 1548, the mining potential of the region was recognized by the discovery of Juan Rayas of the Veta Madre de Guanajuato, known today as La Mina de Rayas.

The majority of silver and other minerals that are extracted from the mines of this region belong to three lodes, which are lodged in faults: La Veta Madre (the Mother Lode), discovered by Rayas, La Sierra (the Sierra) and La Luz (the Light). These lodes run almost parallel in a northeast, southwest orientation. The BASE (ground) of the area is made up of sedimentary and volcanic-sedimentary metamorphosed rock. In 1905 L.J. Burckhardt proposed in his book ‘LA FAUNE MARINE DU TRIAS SUPERIEUR DE ZACATECAS’ that these lodes date back to the Upper Triassic Period, according to their relation those of the Zacatecas area.

The mineralogy of the area is very simple, with selenium being outstanding. Petruck and Owens, in their report published in 1974, listed sulphides such as pyrite, marcasite, acanthite, polybasite, pearceite, chalcopyrite, galena, pyrargyrite, terahedrite, and arsenopyrite; metals such as gold, silver and electrum; selenides such as aguilarite and naumannite; silicates such as quartzes, ANDULITE or chlorite; carbonates such as calcite, dolomite and siderite. The most abundant being pyrite, ARGENTITAS, polybasite, electrum, galena and chalcopyrite. These minerals grow in the most marvellous formations, which four hundred years ago called the attention of the first explorers who imagined something that turned out to be a reality: that they were truly standing in a land full of treasure and opportunities.

Tiro de San Juan Rayas

Calcite on Amethyst from San Juan Rayas, Guanajuato, Mexico.Luis Lyons photo