Gold mineralization in the El Gallo 1 mine area occurs in six deposits along two distinct structural trends, northwest and northeast. A northwest trending structural zone hosts the Samaniego and San Rafael deposits. San Dimas also is hosted by a northwest-striking structure. The second structural trend is northeast-striking and includes the Sagrado Corazón, Lupita and Central deposits. Along these structural trends the mineralization is located within numerous sub-structures that may be parallel, oblique or even perpendicular to the principal trends. Mineralization among the various deposits of the El Gallo 1 area is generally similar, with the individual structural zones consisting of quartz stockwork, breccia, and local quartz vein mineralization occurring within propylitically altered andesitic volcanic rocks. The Samaniego, San Rafael, Lupita, Sagrado Corazon and Central deposits are characterized by gold accompanied by iron oxide and variable copper; the San Dimas deposit is polymetallic containing gold, silver, copper, lead and zinc.

By the end of Q2 2018, mining and crushing activities at El Gallo ceased and were followed by residual heap leaching. Closure, reclamation and residual heap leaching activities are ongoing and will continue for several years.

At the El Gallo 1 mine, mineralized material is processed using heap leaching. Heap leaching consists of stacking crushed, oxidized material on impermeable pads, where a weak cyanide solution is applied to the surface of the heap to dissolve and leach the gold and silver. The gold and silver-bearing solution is then collected and processed into doré bars.