The Don David Gold Mine (DDGM) area is predominantly volcanic rocks of presumed Miocene age, which overlay and intrude into basement rocks consisting of marine sediments. This district's gold and silver mineralization is related to the volcanogenic system and is considered epithermal in character.

The DDGM mineralization occurs as structurally controlled epithermal deposits in veins and stockwork zones. The mineralization is associated with gangue minerals such as quartz, calcite, and other minor elements. Primary sulfide mineralization consists of pyrite galena, sphalerite, chalcopyrite, and different minor amounts of argentite and silver sulfosalts. It consists of concentrations of sulfides containing gold, silver, lead, copper, and zinc.

DDGM exploration efforts have been mainly focused on the Arista Project, which contains the Manto Vein, Arista, and Switchback vein deposits, and includes the significant Arista, Baja, and Soledad veins as well as multiple ancillary structures. The principal hosts of mineralization are the Arista and Switchback vein systems, known from drilling and underground workings in the Arista underground mine. The Switchback deposit is approximately 500 m northeast of the Arista deposit. Both vein systems are andesitic host rocks, rhyolite dikes, and structural contacts with the basement sedimentary rocks. The mineralization in these systems is intermediate sulfidation with precious and base metals at economic grades. Both vein systems trend northwesterly; although locally, vein orientations can range from north-south to eastwest.

The second zone of interest is the Alta Gracia property, where low sulfidation epithermal, predominantly silver mineralized, veins are hosted in andesitic and rhyolitic rocks; this property has been investigated by drilling and surface and underground mapping of historical and recent workings. The Mirador and Independencia vein systems, which DDGM has mined, are one of several predominantly northeast trending vein systems on the property.

Other mineralized zones and properties have been investigated, including some preliminary drilling in areas such as Escondida, Chacal, and Salina Blanca on the Arista Project and the Margaritas and Rey properties. The Margaritas and Rey properties host low sulfidation epithermal veins with volcanic associations.

Historically, companies have produced ore from two locations on the Arista mine, the open pit mine and the underground mine. The open pit mineralization is considered low sulfidation, epithermal mineralization primarily of gold with some silver and no base metals. In 2021, mining activities were completed in the open pit, and it will now become the site for filtered dry stack tailings deposition. The Arista underground mine is considered intermediate epithermal mineralization of gold, silver, copper, lead, and zinc. The host rock in the Arista vein system is primarily andesite.

Conventional drill and blast methods are used to extract the Mineral Resources from the Arista mine at the Aguila project.

There are two main mining methods used in the Arista mine: 1) overhand mechanized cut and fill (CAF) and 2) long-hole open stoping (LHOS) with delayed fill. Paste fill, cemented rock fill and uncemented rock fill are applied to long-hole stoping areas in order to increase extraction levels (removal of rib pillars), CAF uses uncemented rock fill as a backfill method.

For the stoping methods, a crosscut from the main ramp intersects the vein, from which an initial drift is excavated perpendicular in both directions along the strike length of the vein. Once the economic limits of the vein have been reached the production cycle starts.

Overhand Mechanized Cut and Fill (CAF)
A CAF stope is started by means of a short (40 to 60 meter) negative 15 percent access ramp usually in the footwall of the vein to provide access to the bottom of the mining block. The ore is then mined in 3-meter horizontal slices using a Jumbo drill. The jumbo will drill 4-meter long essentially parallel and horizontal 1-3/4-inch holes that will later be charged with explosives to “breast down” and break the ore.

The length of these mining blocks can vary from 50 to 250 meters in strike length. After the first slice or cut is complete, the void will be filled with loose waste rock to form the floor of the next cut. Access to the second and subsequent cuts is gained from the access ramp by changing its grade to reach the higher elevation.

For CAF stoping, upper holes are sometimes drilled using a jackleg. In this case, geologists will mark up the vein, and the stope is drilled and blasted accordingly. In some cases, the drill holes on the vein are blasted first. After the ore has been mucked, the holes drilled in waste are then blasted to achieve the dimensions required to work in the next production lift.

Long Hole Open Stoping (LHOS)
DDGM targets to longhole open-stoping as its primary long-term stoping method.

The mineralized vein is developed with the assistance of an electric hydraulic drill or jumbo. The size of the tunnel is 4.0 meters in height with a minimum width of 3.2 meters to accommodate mining equipment. Ground or rock support is applied in the vein development to match the rock or ground condition as specified by the staff rock mechanic engineer. This artificial support can be spilt set bolts, resin rebar bolts, screen and /or shotcrete. The ore development or drill levels have a 20-meter floor to floor interval. The mineralized vein is broken by means of drilling 3-inch diameter holes from the top level to the bottom levels. The drill length is approximately 14 meters, depending on the angle or dip of the vein. These drill holes are then charged or loaded with explosives and detonated. The broken rock is then extracted from the bottom level with a 6- yard articulated loader or scoop. For safety reasons, the scoop is operated remotely at a safe distance from the brow of the open stope and any rock that could slough off from the walls. As mining progresses in a bottom up sequence (lower level first), the lower mining block is filled with paste fill or loose waste development rock, to form the floor of the next stope. The stoping sequence will then be repeated on the mining block above the lower now mined out block.

For longhole open stoping DDGM utilizes a Stopemaster HX longhole drilling machine.

Backfill Method
DDGM uses two kinds of backfill; waste rock backfill generated during underground mining and paste fill. Since the introduction of paste back fill in 2019, it totally replaced the use of CRF. All primary Stopes uses pastefill and waste rock is used on Secondary stopes, longitudinal stopes and other stopes that don’t need a free-standing face to mine next to them.

Produced ore from two locations on the Arista mine, the open pit mine and the underground mine. The open pit mineralization is considered low sulfidation, epithermal mineralization primarily of gold with some silver and no base metals. In 2021, mining activities were completed in the open pit, and it will now become the site for filtered dry stack tailings deposition. The Arista underground mine is considered intermediate epithermal mineralization of gold, silver, copper, lead, and zinc. The host rock in the Arista vein system is primarily andesite.

Crushing and Milling
Crushing is a dry process which begins at the reception hopper, where ore from the mine is deposited. The maximum size of rock that can be fed to the crushers is a nominal 635 mm. The primary crusher is a 0.91 m X 0.51 m Pioneer jaw crusher. The crushed ore is transferred via conveyors to a 3-deck MCA vibrating screen with dimensions of 1.83- X 6.10-m per deck with the oversize from screening conveyed to a secondary 1.52-m Pioneer cone crusher, where the final product for milling is reduced to -95 mm. The maximum crushing rate for this plant is about 110 tonnes per hour. The fine ore is stockpiled before being fed into the crusher and ball mills.

The fine crushed ore is transported via conveyor belts to the flotation plant grinding circuit. The grinding circuit consists of an Allis-Chalmers 3.04- x 4.27-m ball mill, and a 15-inch cyclone classifier. The ball mills are filled with 38 % of their volume with 3-inch wrought steel balls used to further reduce (grind) the ore size. The product of the mill is pumped to the classification process comprised of hydro cyclones, where two products are generated; 1) a fine ore, which is expulsed thorough the top of the cyclone, and 2) a coarse ore that exits through the bottom and is recycled back into the mill for further grinding. The fine ore must comply with the metallurgical conditions for metal recovery, which indicates 55% of the product must be under the 200 mesh size (equivalent to 74 microns), before being sent to the flotation process.

GRC has also improved two areas of the crushing and milling. In 2013, a Knelson Concentrator gravity circuit was installed to help improve gold recovery. In addition, the mill was expanded to a nominal 1,500 dry tonnes per day employing the same process and generally the same equipment types as described above. The expansion included doubling the amount of flotation cells and thickener surge tanks and the addition of a second ball mill on the flotation circuit. In 2019, an increase in pumping capacity to the cyclones resulted in plant capacity increasing to 1,800 tpd.

The processing plant has a differential flotation circuit capable of processing polymetallic ores and producing up to three separate concentrate products for sale and an agitated leach circuit capable of producing gold and silver doré for purchase. The DDGM mill flotation circuit and agitated leach processing capacities are a nominal 2,000 tpd.

DDGM currently mills and processes the Arista and Switchback underground mines ore through the flotation circuit at the DDGM Processing Facility. The Don David Gold Mine processing plant was built near the mine site and consists of both a sequential flotation (sulfide) circuit and an agitated cyanide leach (oxide) circuit. The flotation circuit produces three separate concentrate products (gold-copper, silver-lead and zinc) from polymetallic ore extracted from the Arista/Switchback underground deposits. The agitated cyanide leach circuit processes ore mainly from the Manto Vein open-pit. The Manto Vein open pit was depleted in May 202 ........