San Martin lies in the Central Mesa between two major geologic provinces, Sierra Madre Occidental and Sierra Madre Oriental. The main sedimentary rock-formation in the San Martin district is the Upper Cretaceous Age Cuesta del Cura limestone. The formation is an interlayered sequence of shallow marine limestone and black chert, and it is overlain by Indura formation which outcrops at the foot of the topographic heights of the Cuesta del Cura formation. It consists mainly of alternating shales and fine-grained clayed limestones in ten to thirty centimeter thick layers.

The district’s most important mineral deposits are replacement veins and bodies generated in the skarn by Cerro de la Gloria granodiorite intrusion. An extensive zone of skarn west of the intrusive hosts, the San Marcial, Ibarra and Gallo-Gallina main ore veins, which appear at the surface for distances of up to 1,000 meters, with thicknesses of 40 centimeters to four meters, paralleling the intrusive contact. In the central part of the deposit there is a horizontal zoning with respect to the contact of the intrusive with high values of silver and copper. In the top of the deposit there is mostly lead and zinc. In the northeast/east over concentric structures to the intrusive there is an increment of lead, zinc and silver in the skarn. Economic ore is found as replacement ore bodies between the main veins as massive and disseminated sulfides with widths from eight meters up to 200 meters. These bodies consist mostly of chalcopyrite (CuFeS), sphalerite (ZnS), galena (PbS), bornite (Cu FeS ), tetrahedrite (CuFe Sb S ), native silver (Ag), pyrrite (FeS), arsenopyrite (FeAsS) and stibnite (Sb S ). Molybdenum and tungsten are found in little portions in the skarn near the contact associated with the calcite.

The horizontal cut-and-fill mining method is used at the San Martin mine.

The broken ore is hauled to the underground crusher station. The ore is then brought to the surface and fed to the flotation plant to produce concentrates. The flotation plant has a total capacity of 4,400 tons of ore per day. The lead concentrate is treated at a third party refinery in Mexico. Copper concentrate is treated at the La Caridad smelter and zinc concentrate is treated at the San Luis Potosi zinc refinery or zinc concentrate is sold to third parties.