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)


  3Q21 2Q21 % change 3Q20
Iron concentrates processed (t) 37,376 48,523 (22.9) 43,871
Silver (oz) 143 167 (14.8) 221
Gold (koz) 441 721 (38.9) 837
Ore grades        
Silver (g/t) 157 147 6.3 212
Gold (g/t) 1.35 1.56 (13.6) 1.87


  • Quarterly silver production decreased 14.8% vs. 2Q21 due to a lower volume of ore processed, mitigated by a higher ore grade of pyrite concentrates processed from the Saucito mine and increased recovery rate.
  • Quarterly silver production decreased 35.6% vs. 3Q20 due to a lower volume of pyrite concentrates processed and a lower ore grade of pyrite concentrates processed from the Saucito mine.

  • Quarterly gold production decreased 38.9% and 47.3% vs. 2Q21 and 3Q20 respectively due to a decreased volume of pyrite concentrates processed, a lower ore grade and recovery rate.

  • Year-to-date silver and gold production decreased 38.5% and 30.1% vs. YTD20 respectively due to lower ore grades from Saucito’s flotation plant, and to a lesser extent, lower recovery rates.
  • As a result of the lower volumes processed at Saucito, and the lower tailings processed at the pyrites plant, we expect silver production to be in the range of 550 to 600 koz for the year while gold production is expected to be in the range of 2 to 2.5 koz.
  • As noted in previous reports, the Pyrites Plant (phase II) was completed in 4Q20 but due to Covid-19 related delays and certain additional technical requirements by the authorities, permits have been delayed. Conversations with Comisión Federal de Electricidad (CFE) and the regulatory authorities have now resumed and we expect inspections to occur in 4Q21 followed by a six week period for commissioning and testing before ramping up the plant.