Mineral Deposit Types
The San Jose de Gracia and Alta Gracia gold-silver sub-districts of the Don David Mine are characterized by classic, high grade silver-gold, epithermal vein deposits with low to intermediate-sulfidation mineralization quartz-adularia-sericite alteration. The veins are typical of most epithermal silver-gold vein deposits in Mexico with respect to the volcanic or sedimentary host rocks and the paragenesis and tenor of mineralization. The Alta Gracia mineralization is typical of a low sulfidation deposit. The Arista mine vein systems are intermediate-sulfidation in nature and standard of many Mexican deposits, characterized by Camprubí & Albinson, 2007, and described as Polymetallic Ag-Au by Corbett.

Description of Mineralized Zones
The Don David Mine mineralization occurs as structurally controlled epithermal deposits in veins and stockwork zones consisting of concentrations of sulfides containing gold, silver, lead, copper, and zinc, associated with gangue minerals such as quartz calcite and other minor minerals. The economic mineralization at the Arista Mine is gold, silver, copper, lead, and zinc. Structurally controlled epithermal veins and stockwork zones at Alta Gracia Project (Mirador Mine) contain mainly silver-gold bearing sulfides. The economic mineralization currently exploited at the Alta Gracia Project is only gold and silver.

Primary sulfide mineralization within the mineralized structures contains pyrite, gale ........

Conventional drill and blast methods are currently used to extract ore from the Arista underground mine. There are two main mining methods used in the Arista underground mine: 1) overhand mechanized cut and fill (“CAF”) and 2) long-hole open stopping (“LHOS”) with delayed fill.

DDGM has advanced the primary decline ramp down to Level 28, approximately 4,400 meters ramp distance from the mine portal. DDGM has also constructed a safety/ventilation decline ramp in conjunction with the primary decline ramp along with various drifts, raises and stopes encompassing approximately 500 m vertically and 1,300 m along strike length.

Access to the mining areas is provided mainly by ramps. Mine development headings are either drilled by jumbo or by jackleg. The dimensions of the different development sections are as follows:
• Main Ramps: 5. W x 5 H meters
• Accesses: 4.5 W x 4 H meters
• Sill in Mineral 4.5 W x 4 Hmeters (if wider width of structure)
• Raise: 2 x 2 meters
• Bore Holes Raise: 3.1 meters diameter

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

Crushing and Milling
Ore is trucked from the mine and discharged onto ground. Ore is fed in a primary jaw crusher using a front head loader. Crushed ore from the primary crusher is screened onto a double deck screen. The first deck product is crushed by the secondary cone crusher. Crushed material is recirculated to feed the double deck screen. The screen second deck oversized products are crushed by a tertiary cone crusher. The tertiary cone crusher material is also recirculated to the feed of double deck screen. Finally, the double deck fine particle (-9.5mm) is stockpiled before being fed into the ball mills. 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. Grinding circuit consists of two parallel ball mills. Each mill is in close circuit hydrocyclones, with cyclone overflow reporting to flotation circuit. A portion of the cyclone underflow reports to the gravity circuit, while the remainder of the cyclone underflow and gravity circuit tailing reports to the ball mill for further grinding. One ball mill is 3.2m diameter and 4.29m length driven by 798 kW motor. The second ball mill is 3.2m diameter and 3.68m length driven by 597 kW motor.

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