Pyrites Plant

Ownership: 100% Fresnillo plc
Location: Zacatecas, Fresnillo District
Facilities: Leaching plant (Saucito mine), flotation plants (Saucito, Fresnillo mines)
Commercial Production: 2Q18 (phase I), 2H20 (phase II)
Anticipated Production: Annual average 3.5 moz silver and 13.0 koz gold
Capex: US$ 155 million

The Pyrites plant is expected to improve overall recoveries of gold and silver, and therefore maximise production in the Fresnillo district; expected to total an average of 3.5 moz silver and 13 koz gold per year once both phases are operating at full capacity.

This project was divided into two phases, the first phase consisted of the iron flotation circuit and pyrites leaching plant at the Saucito mine, which was commissioned mid-2018. The second phase, a 14,000 tpd tailings flotation plant at the Fresnillo mine, is under construction and is expected to be concluded in 2H20. 

The second phase, a flotation circuit, will treat the ongoing and historical tailings from the Fresnillo mine to produce a pyrites concentrate which will be sent to a filtration plant and then on to the leaching plant at Saucito, the final part of the process to produce the precipitates. Commissioning of phase II of the Pyrites plant set for 2H 2020.

Pyrites Plant (Phase I)


  1Q22 4Q21 % change 1Q21
Iron concentrates processed (t) 32,364 31,976 1.3 41,760
Silver (oz) 150 121 24.6 137
Gold (koz) 510 455 12.2 678
Ore grades        
Silver (g/t) 193 158 21.8 143
Gold (g/t) 1.59 1.39 14.1 1.64


  • Quarterly silver and gold production increased 24.6% and 12.2% vs. 4Q21 respectively due to higher ore grades from the Saucito flotation plant.
  • Quarterly silver production increased 9.9% vs. 1Q21 due to a higher ore grade from Saucito’s flotation plant, and to a lesser extent, higher recovery rate, partially offset by a lower volume of pyrite concentrates processed from the Saucito flotation plant.

  • Quarterly gold production decreased 24.7% vs. 1Q21 due to a lower volume of pyrite concentrates processed.

  • In 2022, we continue to estimate silver production from the Pyrites plant at Saucito to be in the range of 700 to 750 koz while gold production is estimated to remain in the range of 1.5 to 2.5 koz.
  • As noted in previous reports, the Pyrites plant (phase II) was completed in 4Q20 but as with Juanicipio, we are focusing on complying with the new requirements from the state-owned electrical company and the energy regulator to complete the tie-in to the national power grid. We continue to expect this by mid-2022.