The Media Luna deposit is located on the south side of the Balsas River, ~7 km south south-west of the ELG Mine Complex.

Systematic drilling has identified a gold-copper-silver mineralized skarn with approximate dimensions of 1.4 km x 1.2 km and ranging from 4 m to greater than 70 m in thickness. The mineralization occurs in most parts around 500 m below surface but crops out at surface at the north side of the Media Luna ridge. Skarn alteration and associated mineralization is open on the east, southeast, southwest, and northwest margins of the area.

The surface geology of the Media Luna area is dominated by Morelos Formation limestone, which is intruded by numerous porphyry dykes and sills. The contact between the Morelos Formation and the El Limón granodiorite stock is exposed in the northern sector of the area, and Mezcala Formation sediments are present in the southern portion of the area. Morelos Formation limestone is typically converted to grey to white marble along with the intrusive contacts, often accompanied by clay and iron-oxide. The Mezcala Formation is locally converted to biotite–hornfels where cut by dykes and sills. The mineralization hosting skarn occurs at the contact of the El Limón granodiorite with the Morelos limestone. The skarn, like the wall rocks, is intruded by numerous porphyritic dykes and sills.

Media Luna is a magnesian skarn and has formed where rocks are more dolomitic, whereas ELG is a calcic skarn. Reflecting the protolith, a calcic skarn contains garnet, pyroxene, and pyrrhotite, whereas a magnesian skarn contains Mg-rich minerals like olivine, periclase, chondrodite, phlogopite, ludwigite, vesuvianite, talc, serpentine, and magnetite. This difference in mineralogy has several important implications. First, the magnesian protolith enables the formation of Mg-rich minerals and forces the iron that would have gone into garnet and pyroxene in a calcic skarn system, to precipitate as magnetite. In a calcic skarn, the excess iron will precipitate as pyrrhotite in a reduced system or pyrite in a more oxidized system. Second, precipitation of magnetite at relatively high temperature means that the available sulfur that would have gone into pyrrhotite formation can precipitate Cu as chalcopyrite from fluids that are present in the skarn environment. This explains why, although the gold contents of ELG and Media Luna are similar, Media Luna has significant Cu, whereas ELG does not.

Across the entire Media Luna deposit, gold is geochemically strongly correlated with bismuth and tellurium. Gold commonly occurs as native Au as well as gold-rich electrum. Chalcopyrite is the principal Cu mineral in the deposit. The Zn–Fe–S system is represented by sphalerite, sulfosalt, galena and Ag-Fe–S rich minerals, such as argentopyrite.

Sulphide minerals including pyrrhotite, chalcopyrite and sphalerite, as well as native metals and bismuth minerals, are intergrown with retrograde amphibole and are thought to have formed shortly after or at the same time as amphibole. There are areas of early pyrrhotite that have patches of ragged and porous-looking pyrite; some even show lamellae of marcasite forming in pyrrhotite. Late pyrite appears to be associated with darker colored chlorite, typically yellowbrown to brownish-green. Chlorite commonly occurs along with garnet or pyroxene grain boundaries or as cross-cutting veinlets with calcite. Late pyrrhotite and pyrite appear to have formed under a reduced state of oxidation.

In general, elevated gold grades (Au-As, Au-Bi) are found in the hanging wall of the skarn package, and copper mineralization dominates along the footwall. These domains commonly overlap near the major dykes. This zonation is more evident on the central-south portion of the deposit. Zn rich domains are constrained to the northern edge of ML and associated with dykes. These dykes are currently interpreted as the main feeders of the mineralization at the deposit scale.

Generally, the skarn contacts are very sharp, with a transition zone of only a few centimeters. Minerals at these locations are very fine-grained and almost impossible to identify in hand samples. Moving across the contact from veined marble to skarn, the mineralogy is dominated by phlogopite and magnetite for 2 to 10 cm before visible pyroxene and garnet appear.

The ML Mineral Reserve is divided into two relatively distinct zones; MLL and MLU. The mine design uses primarily LHS with paste backfill and some MCAF stoping. The mine design provides operational flexibility for planning and scheduling while targeting high grade material early in the production life. The mine design divides the mine into blocks which can operate as independent areas but share a main access and materials handling system to transport mineralized material under the Rio Balsas to the ELG Process Plant.

Media Luna will be accessed via three portals and tunnels: Guajes portal and tunnel on the north side of the Rio Balsas at the ELG Mine Complex and South Portal Upper (SPU) and South Portal Lower (SPL) portals and tunnels on the south side of the Rio Balsas near San Miguel. There are box cuts and portals constructed at each site to facilitate tunnel development and the life of mine operation. The plan to maintain the ELG Mine Complex as the main access route provides benefits from a social, environmental, security and operational perspective.

Guajes Tunnel
The Guajes Tunnel will be the main haulage route for life of mine operation and the primary access for personnel and material movement from surface to underground.

The Guajes Tunnel profile is 6.0 m wide by 6.5 m high and is approximately 6.5 km long with a maximum gradient of 13%. For the development phase, one 1,830 mm diameter and one 1,520 mm temporary ventilation ductwork will be suspended from the back and will accommodate clearance for a loaded 45-t class haul truck. Remuck bays with truck loading will be established every 150 m. Safety bays will be developed every 60 m and passing bays every 300 m.

The Guajes Tunnel is currently being developed and as of December 31st, 2021 approximately 1,033 m have been completed.

South Tunnels
The south tunnels were selected as early mine accesses to ML and for LOM ventilation and paste backfill delivery. There are two portal locations for the south tunnels, SPL at 990 meters above mean sea level (MAMSL) and SPU at approximately 1,105 MAMSL.

The SPL tunnel profile is 5.0 m wide by 5.5 m high at a maximum gradient of 15%. For the development phase, temporary 1,520 mm diameter ventilation ductwork will be suspended from the back and will accommodate clearance for a loaded 30-t class haul truck. Remuck bays with truck loading will be established every 150 m. Safety bays will be developed every 60 m and passing bays every 300 m. The SPL tunnel is currently being developed and as of December 31st, 2021 approximately 233 m have been completed.

The SPU main tunnel profile for the initial 460 m is 5.5 m wide by 6.0 m high at a gradient of -2.0 % until it reaches the intersection with the SPU ramp at which point both tunnels will be 5.0 m wide x 5.0 m high. The South Portal main tunnel continues at a gradient of -2.0 % while the SPU ramp is developed at a minimum gradient of -15%. For the development phase, temporary 1 520 mm diameter ventilation ductwork will be suspended from the back and will accommodate clearance for a loaded 30-t class haul truck. Remuck bays with truck loading will be established every 150 m. Safety bays will be developed every 60 m and passing bays every 300 m. The SPU main tunnel is currently being developed and as of December 31st, 2021 approximately 333 m have been completed.

The primary mining method selected for Media Luna is LHS with paste backfill. LHS provides a high production rate and lower operating cost based on the resource geology and overall good rock mass quality. There are two types of LHS in the mine design: transverse stoping and longitudinal retreat stoping. The limit between transverse and longitudinal retreat stoping is a stope thickness of 12 m, but stopes in close proximity are also taken into account. For example, if a stope is 15 m wide but surrounded by other longitudinal retreat stopes it would match that stoping method and be recovered longitudinally. Wherever possible, mining would progress from the bottom up. In areas where the Mineral Resource is not continuous for LHS, overhand MCAF stoping will be utilized. Based on the mine design, MCAF accounts for 4% of the total production.

Preliminary mining stope shapes were estimated using the Deswik Shape Optimizer (DSO). The range of stope dimensions evaluated were first constrained by geotechnical parameters. This work resulted in a nominal stope size using a 25 m (vertical) level interval, 20 m wide by 30 m long. Other level intervals that were trialed were 20 and 30 m along with stope widths of 25 m. There is a possibility that varying the level interval level-to-level depending on resource geometry will provide better resource recovery. For the feasibility study it was determined that a consistent level interval would be more appropriate due to the resource definition and the base stope size remained 25 m high (vertical) by 20 m wide by 30 m long.

Longhole Stoping (LHS) would be the main mining method employed and the LHS methods would be transverse stoping, transverse up-hole stoping, longitudinal retreat stoping, and longitudinal retreat up-hole stoping.

Most stopes would be accessed using undercut and overcut development (all non-up-hole stopes). Production drilling along with loading and blasting would take place from the overcut. Mucking of blasted material would occur from the undercut, while backfill would be placed in the open stope from the overcut. For the up-hole stopes, all activities would take place from the undercut.

There are some stopes located in weak ground. These stopes account for less than 2% of the stopes. The weak ground stope would be unstable and special pre-cautions would have to be in place during the mining of these stopes. These stopes would have no personnel access during stoping, with all drilling, blasting, and mucking conducted remotely, this can be achieved with fan drilling from the footwall drift or other drift parallel to strike in good ground.

In small areas where the resource is not consistent for LHS, an overhand MCAF method would be utilized. The MCAF stope areas would occur later in the mine life when stoping tonnes and waste development is ramping down. The development crew would transition from lateral development for LHS to MCAF This will result in the recovery of more ore and a smoother ramp down.

The height and strike length of stopes will be consistent throughout the mine design; however, the distance from hangingwall to footwall of stopes and stope dip will vary. For the two types of LHS, an average distance HW to FW and dip was used to define an average stope size for each longhole method.

For LHS, when the overcut and undercut development is complete, slot raises will be drilled using an in-the-hole (ITH) drill and a Machine Roger V30 reaming head (or similar). Most slot raises will be developed top-down, but some will use a blind boring up-hole for the up-hole stopes. An initial pilot hole will be drilled and reamed followed by the installation of the reaming head and a second pass of reaming to the final diameter of 762 mm (30 inches). For transverse stopes these slots will typically be 20 m long and for longitudinal retreat the length would be approximately 24 m.

The process will make use of the existing ELG grinding circuit, agitation leaching, SART, ADR and part of the tailing facilities. During the overlap period when both ML ore and ELG ores are available, these will be processed either in a blend of ML/ELG UG and ELG OP ores or ELG OP ores by themselves. Metallurgical testing indicates that minor blending of ELG OP ores with ML and ELG UG ores does not negatively affect the copper flotation process.

A new conveyor suspended from the tunnel back will transport material from the Guajes Tunnel directly to the ELG plant area from the ML Underground workings. The ML material will be stockpiled separately from the ELG ores. Blending or batching will be dependent on the mine production when in operation. The mineralized ores will be fed through the existing Guajes gyratory crusher and then fed to the existing coarse ore stockpile and grinding circuit. After grinding, the ML ore will pass through a copper sulphide rougher and then a Fe ........