The San Ignacio underground gold-silver mine is located in Guanajuato State in Mexico, which hosts three of the ten biggest silver mines in the world. Great Panther owns the mine through its Mexican subsidiary, Minera Mexicana El Rosario.
The project received an environmental permit in October 2013 and began commercial production in June 2014. It currently processes ore at a rate of approximately 200t a day, which is expected to increase to 250t a day in future.
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San Ignacio mine location, geology and reserves
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San Ignacio mine consists of a block of seven conterminous mineral claims covering 324.7ha. It lies within the Guanajuato Mining District and covers approximately 4km of strike length on the La Luz vein system. The mining district is located within the Mesa Central physiographic province, which hosts rocks comprising a Paleocene to Pliocene sequence of dacite-rhyolite, andesite and basalt.
The San Ignacio property is located above a group of basalt (Kbas) and andesite (Kanlf) volcanic rocks of Cretaceous La Luz andesite, forming part of the volcanic-sedimentary complex featuring varied tectonic interpretations.
Mineralisation at the gold-silver project occurs in epithermal silver-gold veins, which form part of the north-west-trending Cenozoic-age faults. The mineralisation occurs within tabular veins, vein stockworks and breccias.
The deposits are classified as classic fissure-hosted, low-sulphidation epithermal gold-silver-bearing veins and stock-works.
According to April 2014 estimates, the San Ignacio mine is estimated to contain indicated mineral resources of 103,000t grading at 165g/t gold and 3.54g/t silver. It is estimated to contain 1.25 million ounces (Moz) of silver equivalent. Inferred mineral resources are gauged at 737,000t at an average grade of 115g/t silver and 2.04g/t gold, equivalent to 5.64Moz of silver.
Mining and processing of gold-silver ore in Guanajuato State
The underground mine at San Ignacio is accessed via a surface portal and the ore is mined using the standard cut and fill method. The run-of-mine ore is trucked and processed at the Cata processing plant at the main Guanajuato Mine Complex.
The ore passes through three-stage crushing via a Pettibone primary jaw crusher, a secondary cone crusher and a Norberg HP300 tertiary cone crusher. The crushed material is conveyed to one of the three Denver ball mills operating in parallel.
The grinding section reduces the fine ore to slurry with 68% of particles passing 74 microns and liberates the sulphide minerals containing the gold and silver from the waste material. The existing flotation section is equipped with five new fully automated Outotec cells.
The products from the flotation cells are sent to cleaning cells as per their quality or circulated again with scavenger products and cleaner tails for regrinding. After cleaning, the concentrate is transferred to the concentrate thickener section and filtered to remove excess water. The concentrate is then sent to the point of sale.
San Ignacio’s construction and infrastructure facilities
Major works at San Ignacio included the construction of ancillary surface infrastructure such as the 2km-long access road, waste dump pad and installation of other mechanical equipment. A diesel storage facility and an electrical substation were also constructed to support the operations at the site.
Electric power for the mining operations is to be supplied from the Mexican national grid.
Key players involved with the development of San Ignacio
MFW Geoscience was engaged to conduct the mineral resources estimate and prepare the National Instrument 43-101 (NI 43-101) Technical Report for the San Ignacio property.
SGS Minerals Services was contracted to analyse the underground mine samples and drill-core samples, in order to prepare the technical report.
