Gold Fields’ Cerro Corona operation is located in northern Peru, in the Cajamarca Region. It operates an open pit mine and a copper-gold flotation processing plant.

Since approximately 2019, ore has been accumulating in stockpiles awaiting processing after open-pit blasting. Once blasted and stored, this material remains exposed to environmental conditions, initiating a natural process of degradation and acidification.

Over time, exposure has shown negative effects on both copper grades and the metallurgical recovery of copper and gold during flotation.

In argillic alterations, the ratios of acid-soluble copper relative to total copper—when they exceed 6%—tend to decrease copper recovery. Additionally, when ore pH values fall below 5.5, losses in copper head grade increase. It has also been observed that longer exposure time increases cyanide-soluble copper. In laboratory tests, some samples show lime consumption increasing up to 15 kg/ton. Losses in copper recovery can reach up to 23%, and in gold up to 10%.

Identified consequences:

- Loss of quality and recovery: reduction in copper grades and decreased copper and gold recovery efficiency.

- High variability and uncertainty: the minerals do not react uniformly to environmental exposure, making it difficult to estimate the quality of the stored material.

- Deviations in production forecasts: significant errors in budget and forecast calculations, affecting economic and operational planning.

- Impact on profitability: part of the value of the extracted ore could be underutilised or lost without even being detected, compromising the metallurgical efficiency and economic performance of the operation.

According to studies by SGS Minerals Services (2011), prolonged exposure of crushed ore to environmental conditions can generate physicochemical alterations that negatively impact its metallurgical performance. In line with these findings, Cerro Corona has developed experimental tests in columns, trays, and barrels to characterise the behaviour of the ore from the pit and evaluate its metallurgical performance after different exposure periods.

Approximately 30 million tons of ore are stockpiled, comprising the five main lithologies of the operation:

- 59% corresponds to potassic alteration

- 22% corresponds to argillic alteration 2

- 12% corresponds to silicified alteration

- 4% corresponds to argillic alteration 3

- 3% corresponds to argillic alteration 1

The results show a trend toward decreasing both head grades and copper recovery, regardless of the lithology. Losses in copper head grades can reach up to 34%, while copper recovery losses reach up to 23%, and in the case of gold, up to 10%. However, these variations do not reach sufficient statistical significance to draw definitive conclusions, highlighting the complexity and variability of the stored ore degradation process.

Reference: SGS Minerals Services. (2011). Aged crushed ore and metallurgical performance (Technical Paper #2009-07) - [link]

A metallurgical recovery model is expected to be developed that can predict losses associated with ore exposure by integrating lithological, mineralogical, and geochemical variables. This tool will optimise metallurgical planning and reduce uncertainty in the operation's economic forecasts.

There is currently no mineralogical model of the stockpile.

Phase 1 - Submission Period

Suppliers are invited to submit their short-form solution to the challenge by Wednesday 4 February 2026 for evaluation by Austmine and Gold Fields.

The solution submission questions can be viewed here.

A shortlisting process takes place and successful suppliers are invited to participate in phase 2.

Phase 2 - Evaluation Period
Shortlisted suppliers will be invited to a technical briefing, where each supplier will be able to gain more information about the challenge from Gold Fields. This will allow you to refine your proposed solution prior to the Pitch Session.

Following the technical briefing, suppliers will pitch their solution directly to Gold Fields online via Teams breakout rooms. This provides the opportunity to ‘sell’ your solution, gain feedback from operational teams and field questions about the solution.

Phase 3 - Full Proposal Submission
Following the Pitch Session, a final shortlisting of supplier(s) takes place. The remaining suppliers are invited to submit their formal technical and economic proposals.

Winner Announced
Gold Fields will select the best fit solution(s) for the challenge. Unsuccessful submitters are notified in writing by Austmine.

Submission deadline - Wednesday 4 February 2026

Shortlisted Suppliers Notified - Wednesday 25 February 2026

Technical briefing - Thursday 5 March 2026 (TBC)

Pitch sessions - Thursday 12 March 2026 (TBC)

Final proposal deadline - Mid March 2026