Grasberg Mine Disruption Threatens 591,000 Tons of Copper Losses Through End-2026
Key Facts
Benchmark Minerals analysis estimated that disruption at Indonesia’s Grasberg mine will reduce copper production by about 591,000 tons between September 2025 and the end of 2026, putting the incident’s impact on supply over that period into focus. The estimate comes as Freeport-McMoRan says the recovery of mining operations in the Grasberg area is proceeding as expected. The company said on October 27, 2026, that it expects significant growth in 2027 and 2028, making the subsequent recovery path central to tracking the disruption’s impact on mine output. Chief Executive Kathleen Quirk said the company had made “steady progress” in ramping up operations. She added that its focus is on “delivering increasing volumes at Grasberg safely and sustainably.”
Production records show the scale of the decline following the incident. The Grasberg minerals district produced about 1.0 billion pounds of copper and 0.9 million ounces of gold in 2025, compared with 1.8 billion pounds of copper and 1.9 million ounces of gold in 2024. Freeport attributed the lower 2025 production to a mudflow incident in September that year. The comparison between the two years offers a view of the disruption’s impact on the mine’s two main metals, as both copper and gold output fell. Benchmark’s estimate for the period from September 2025 through the end of 2026 also places the expected additional impact on copper production within a defined timeframe.
The incident occurred on September 8, 2025, when about 800,000 metric tons of wet material entered the underground Grasberg Block Cave mine and quickly moved to different levels, according to the Associated Press. The source described the event as a flow of material inside the mine; the stated quantity refers to the material that entered it, not an estimate of the damage. The incident matters in the context of subsequent production, as the company linked the Grasberg district’s lower 2025 output to the September mudflow. In October 2026, Freeport said the pace of its operational ramp-up had met expectations, with significant growth anticipated over the following two years. This links the production impact reflected in 2025 figures with the recovery path the company later described.
At the company level, consolidated sales in the third quarter of 2026 were about 749 million pounds of copper and 105,000 ounces of gold, according to Freeport’s results. The company estimated 2026 sales at about 3.0 billion pounds of copper and 649,000 ounces of gold. These figures provide a measure of the company’s quarterly sales and its annual estimate, alongside Grasberg production data comparing 2025 with 2024. The consolidated sales figures do not mean the sales came from Grasberg alone, as the company presented them across its consolidated business. The estimated loss of 591,000 tons therefore remains tied to the analysis of the mine disruption, while the sales figures describe a broader scope of Freeport’s operations.
Freeport said the average realized copper price was $6.54 per pound in the third quarter of 2026, while the average consolidated cash cost was $2.07 per pound over the same period. The two figures are company-wide average realized price and cash cost measures, not prices specific to Grasberg production alone. In the market reaction when the incident emerged, Freeport shares fell more than 13% to $39.31 at midday trading on September 24, 2025. Copper futures rose 3.8% to $4.82 per pound at midday trading in the same session, according to the Associated Press. That day’s trading showed a divergence between the share-price decline and the rise in futures, as news of the mine disruption drew attention to its impact on company production and supply.
The next operational steps include upgrades to the materials handling system at Grasberg Block Cave, which Freeport said are on track for completion in early 2027. The company is also continuing preparations to restart the 1S production block by mid-2027. Both dates precede the company’s expectation of significant growth in Grasberg district operations during 2027 and 2028, while it said in its update that recovery is proceeding as expected. Restarting the block and upgrading the handling system are two announced milestones in the production ramp-up, with the disruption’s impact on output remaining central to Benchmark’s estimate through the end of 2026. Quirk said the company is focused on increasing volumes safely and sustainably as the operational ramp-up continues.