The Mulatos mineral deposits are large epithermal, high-sulfidation, disseminated gold deposits. Gold mineralization is closely associated with silicic alteration within extensive areas of argillic and advanced argillic alteration. The Mulatos deposit proper is composed of the contiguous Estrella, El Salto, Mina Vieja, and Puerto del Aire Mineral Resource areas. The Escondida deposit is the faulted extension of the Mina Vieja and El Salto sub-deposits and is believed to be continuous to the northeast with the Gap, El Victor, and San Carlos mineralized areas. Although zones are often bounded by post-mineral faults, together they form a trend of 2.7 km of gold mineralization starting at the north end of the Estrella pit to the San Carlos deposit.

Within the larger Mulatos Group of Concessions, and generally within 20 km from the Mulatos deposit, geologically similar high sulfidation gold deposits, occurrences, or prospects are known.

Gold deposits of the Mulatos district are considered to be high sulphidation-state epithermal systems. Epithermal precious metal systems may be classified as high, intermediate, and low sulphidation styles. They are characterized by the sulphidation state of the hypogene sulphide mineral assemblage, and show general relations in volcano-tectonic setting, precious and base metal content, igneous rock association, proximal hypogene alteration, and sulphide abundance. Ore in all occurrences is of the type formed under epizonal co ........

Pre-stripping of the La Yaqui Grande pit commenced in December of 2020. Ore mining started in January of 2022 with some ore being used to produce over liner for the heap leach pad and the remainder being stockpiled until commissioning of the crusher commenced in May 2022. In the fourth quarter of 2022 La Yaqui Grande was mining at its design rate of 10,000 tpd of ore.

Mining is undertaken by a contractor, different from that used at the main Mulatos pit, and is supervised by Mulatos staff. The contractor employs six CAT 992 front end loaders, 21 CAT 777 haul trucks, eight drills and 14 pieces of support equipment. Mining of the La Yaqui Grande open pit is expected to continue through 2027.

The bench height is nine metres, and a catch bench is employed every three benches. The contractor undertakes blasthole and pre-split drilling and explosives are supplied to the hole by an explosive’s vendor. The contractor is also responsible for loading and hauling as well as road, bench, and waste dump maintenance. Survey and ore control are undertaken by Mulatos staff.

The primary waste dump is located to the north of the pit and is generally a relative flat haul, with a number of pit exits accessing the waste dump. The crushing plant is located adjacent to the heap leach pad, and both are west of the open pit and accessed via a downhill haul.

Primary Crusher
Run-of-mine ore (ROM) is trucked from the mine by 100 tonne haul trucks to the crushing plant. The mine trucks normally direct dump onto a stationary grizzly located over the dump pocket. Alternatively, ROM ore may be trucked to a stockpile ahead of the primary crusher and later reclaimed using a front-end loader.

An apron feeder draws ore from the dump pocket at a controlled rate and dumps into a vibrating grizzly feeder with the feeder oversize reporting to the jaw crusher. The grizzly feeder undersize material bypasses the primary crusher and combines with the crusher product on conveyor belt No. 1 (CV-001), which discharges onto conveyor belt, No. 2 (CV-002).

Conveyor belt No. 2 discharges onto a coarse ore stockpile, with a 20,000 total tonne capacity.

A mobile hydraulic rock breaker is provided to break oversize ROM material.

A self-cleaning electric magnet is installed at the conveyor belt No. 1 transfer point to remove tramp metal.

A belt scale is installed on conveyor belt No. 2.

Water sprays are installed to suppress dust in ore feed streams, transfer points, dump pocket, and feeding the jaw crusher.

The crushing facility is equipped with an air compressor and air receiver for equipment maintenance and instruments.

Fine Crushing and Agglomeration
Ore is reclaimed using two variable speed belt feeders, which discharge onto conveyor belt No. 3 (CV-003).

Conveyor No. 3 discharges onto conveyor Belt No. 4 (CV-004), which discharges onto a double deck, vibrating, inclined screen. The undersize fraction from the screen bypasses the secondary and tertiary crushing circuit and reports to conveyor belt No. 10 (CV-010), and then onto conveyor belt No. 13 (CV-013). Oversize material from both decks is dumped directly into the secondary cone crusher.

Secondary crushed ore product is conveyed via conveyor belt No. 5 (CV-005), and conveyor belt No. 7 (CV-007) to a double cone tertiary feed bin. Two variable speed belt conveyors discharge ore onto the double deck tertiary screens.

The undersize fraction from the tertiary screens reports to conveyor belts No. 11 and No. 12 (CV011/012) respectively, which discharge onto conveyor belt No. 13 (CV-013). Screen oversize reports to the two tertiary crushers. The tertiary crushed ore is conveyed back to the tertiary crushing circuit for re-classification via conveyor belt No. 5. The product of the fine crushing circuit, at approximately 80 percent passing 9.5 mm, is conveyed to the agglomeration circuit for the binding process.

Cement and lime are added to the ore on conveyor belt No. 14 (CV-014), which is discharged into a pug mill mixer. The pug mill discharges onto conveyor belt No. 15 (CV-015), which feeds the drum agglomerator. Barren solution is added in the drum to reach the desired moisture for agglomeration. Agglomerated ore is discharged onto conveyor belt No. 16 (CV-016). A series of grasshopper conveyors and a stacker place the ore on the heap leach pads.

A metal detector is installed over conveyor belt No. 3 (CV-003) to manually remove any scrap metal.

Two lime silos and two cement silos are utilized.

A belt scale is installed on conveyor belt No. 13 and provides a signal for adjusting lime, cement addition and water addition to ensure set moisture for agglomeration. A belt sampler is also installed on conveyor belt No. 13.

Water sprays are utilized for dust suppression at the fine crushing circuit.

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