The mineralization at La Parrilla occurs in veins, breccias, stockworks and replacements that are hosted by the Cretaceous limestones and shales of the Indidura Formation and by the granodiorite–quartz monzonite intrusion. Contact metamorphism and metasomatism resulted in the development of marble, hornfels, skarnoid, and skarn at the intrusive contact. Because the mineralization is related to the intrusive contact and skarn development, the deposits are proposed to be of the intrusion related hydrothermal type, and may represent mesothermal to epithermal environments.

Veins at La Parrilla are of two types: open space filling veins and fault-veins. The open space filling veins can consist of massive sulphides veins; quartz-calcite veins containing pyrite, sphalerite, and galena; and breccia veins cemented by quartz-calcite. Fault-veins consists of matrix-supported breccias or gouge containing disseminated sulphides and oxides. Open space filling veins can transition along strike into fault-veins and vice versa, and the presence of stockwork is common at the contacts of the vein with the host rock. Thus, it is interpreted that most veins were open or partially open faults and fractures, that they were flooded with hydrothermal fluids, and that some of these were reactivated by later faulting. Replacement deposits, on the other hand, occur as oblique or perpendicular splays to veins and faults, and as larger replacement deposits concordant with sedimentary bedding. R ........

The La Parrilla Silver Mine is a complex of producing underground operations consisting of the Rosarios, La Blanca and San Marcos mines which are interconnected through underground workings, and the Vacas and Quebradillas mines which are connected via above-ground gravel roads.

The underground mining operations currently use the Mechanized Cut and Fill (MCF) mining method. This is the mechanized version of a classic method for mining narrow orebodies and involves extracting the ore in small slices, 2 to 4 m high, working from the bottom of the mining block upwards. As each cut is extracted, the void is filled with waste rock from development to stabilize the walls and create a working platform for the next lift.

MCF mining for a new mining block begins by driving a 4 x 4m ramp on the footwall side of the ore body and establishing sub-levels at regular vertical intervals. A typical mining block at La Parrilla will have the main haulage levels every 50 m with three sub-levels at 12 m intervals. The main haulage levels will include any ventilation infrastructure, a remuck for storing broken ore, a truck loading area, electrical substations and sumps.

To access the ore body, an initial access drift or attack ramp is driven from the lower main level to near the middle of the bottom elevation of the MCF stope. Typical development methods are then used to drive sill drifts in ore to each extent of the ore body. Sill drifts are typically driven 3.5 t ........

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