Three principal zones of sulfide mineralization have been identified within a broad area of skarn alteration in the vicinity of San Rafael and nearby El Cajón. The San Rafael Main Zone consists of masses of sulfide grains that occur as replacements at an unconformable contact between what is believed to be Tertiary dacite tuff and Cretaceous limestone. Although it can be difficult to determine the host rock when total sulfide content is 90 to 100%, most of the massive sulfide replacement mineralization appears to be hosted in the dacite tuff. It contains silver, lead, and zinc mineralization with lessor gold and copper. The main minerals are pyrite, pyrrhotite, sphalerite, and galena with minor marcasite, chalcopyrite, and magnetite. This mineralization in the San Rafael Main Zone is often associated with quartz-sericite-pyrite alteration that has been interpreted as more distal skarn alteration. It has also been suggested that the San Rafael Main Zone displays many similarities to volcanogenic massive-sulfide deposits, such as those found in the Guerrero Terrane in central Mexico.

Mineralization within the Main Zone at San Rafael is primarily massive, sulfide-replacement material, which can contain greater than 90% sulfides, dominantly pyrite and pyrrhotite. The sulfide body is discrete, tabular, and lies along the shallow-dipping dacite tuff-limestone contact where it has been referred to as “massive-sulfide mineralization” in previous reports. The zinc, lead, ........

Construction started at San Rafael in September 2016 and achieved commercial production in December 2017. The Mineral Reserves support a mine life of five years. The underground mine is accessed by a decline that portals at surface near the southern portion of the deposit where the surface infrastructure is located. A series of ramp systems from the main decline provides access to the various stoping areas of the mine.

The main decline has reached the bottom of the defined Mineral Reserves in the Main Zone and ramp development to access the Upper Zone has commenced. Due to the depth, shallow-dipping angle and variable thickness of the mineralization, the mining method used at San Rafael is post-pillar cut and fill. Stopes are accessed from a primary stope access driven at a -15% decline. After mining of each successive 5m high cut of ore, the stope is backfilled and the access “backslashed” to allow for mining of the next cut. This sequence is repeated up to five times until the stope access reaches an incline of +15%. Access to the next cut is then provided by a -15% stope access driven from a higher elevation. The LOM plan anticipates that the cut and fill stopes will be backfilled with unconsolidated development waste and waste generated from a waste quarry. Given the use of unconsolidated backfill, the mining sequence is typically from the bottom up.

Primary mine ventilation is provided via two vertical bored raises and the main decline. A main exhau ........

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