The Grasberg mine is not a gold-only operation. It is a copper-gold-silver district in Central Papua, Indonesia, on the western half of the island of New Guinea. Its underground Grasberg Block Cave works the same ore body that was previously mined from an open pit on the surface. The “$40 billion” figure is a historical claim tied to the reserves identified after the 1988 discovery. The reviewed official sources do not establish that the mine is worth $40 billion today, and the “world’s largest” ranking is a dated government characterization rather than a current, independently verified ranking.
Where the Grasberg mine is
Grasberg sits in the Grasberg minerals district of Central Papua, a province of Indonesia. Readers should keep this distinct from Papua New Guinea, which is a separate country occupying the eastern half of the same island. Freeport-McMoRan describes the district in its company overview as “one of the world’s largest copper and gold deposits in the Grasberg minerals district in Central Papua, Indonesia.”
The site is remote and high in altitude. PT Freeport Indonesia’s official virtual tour places Grasberg at approximately 4,200 metres above sea level. That tour is an undated page, so treat the elevation as a general description rather than a surveyed figure for any particular working.
Two dates appear in the company’s materials, and they answer different questions. Freeport-McMoRan dates the discovery of the Grasberg deposit to 1988. Mining operations by PT Freeport Indonesia began in 1972. The reviewed sources do not explain the gap between these dates in detail, so avoid merging them into a single story of one mine opening in one year.
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What the deposit contains
Grasberg is a copper-gold-silver deposit. Geological sources describe the district as a porphyry-skarn system, which is why copper is the largest commodity by weight. Gold is valuable enough that it drives much of the headline attention, but the mine is not defined by gold alone.
The company’s most recent reserve statement is in its SEC-filed presentation for year-end 2024. It reports 22 million ounces of gold and 27 billion pounds of copper in consolidated proven and probable reserves. These are reserve quantities, meaning material estimated to be recoverable under stated conditions. They are not a dollar value. The presentation attaches the calculation basis to the figure, describing it as “Estimate of recoverable proven and probable consolidated mineral reserves using long-term average prices of $3.25/lb for copper and $1,600/oz for gold.”
That price basis matters. Reserves estimated at one set of long-term prices will produce a different economic picture if prices change, and the estimate is only as current as its date.
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The “$40 billion” figure
The $40 billion number appears in secondary accounts, including an academic thesis, as a valuation of the reserves identified at Grasberg in 1988. The reviewed sources did not locate a primary, contemporaneous document that explains how that valuation was calculated, which metal prices it assumed, or what it included. Without that information, the number can be reported only as a historical claim attributed to the people who made it.
Two statements should not be made. The first is that the mine is currently worth $40 billion. The second is that the year-end 2024 reserve tonnage implies a $40 billion value. Neither is supported by the official reporting, which gives reserve quantities and assumptions rather than a current valuation.
Reserves and value are different measures. A reserve is an estimate of material that can be recovered economically under stated assumptions. Market value depends on prices, costs, taxes, financing, the remaining life of the operation, and the owner’s share of cash flow. The SEC-filed technical report summary for Grasberg has an effective date of December 31, 2021 and a report date of January 31, 2022. It states that its estimates apply as of the effective date and may be altered by subsequent events and changes in assumptions.
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Is it the “world’s largest” gold mine?
The strongest version of the ranking comes from Indonesia’s Ministry of Energy and Mineral Resources, which called Grasberg the world’s largest gold mine in a 2017 statement. That is a dated government characterization, not proof of a current global ranking.
Freeport’s current company overview uses more qualified language, describing the deposit as one of the world’s largest copper and gold deposits. The reviewed sources did not identify an independent ranking methodology that compares “largest” and “richest” mines across the industry on a current basis. Readers should treat the superlative as an attributed statement from 2017, and the more cautious company wording as the current position.
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The 2017 statement also described a potential life of more than 30 years. Read that as a historical expectation at the time, not a guaranteed remaining life for the mine.
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Surface pit and underground block cave
The “hidden beneath” framing describes a transition in how the ore is reached. The ore body was first mined from the surface in an open pit. Freeport identifies the Grasberg Block Cave ore body as the same body previously mined from the surface. The wider district also contains several distinct underground mines and deposits, so “underground Grasberg” is not a single location.
The historical open pit
The open pit exposed the ore body from above. Its defining feature was surface access, which made the ore visible and directly reachable from the ground. The reviewed sources do not provide a full description of the pit’s final geometry or its current condition, so avoid describing it beyond its role as the earlier phase of extraction.
The Grasberg Block Cave
The block cave works the same ore body underground. The official virtual tour gives an example of depth: about 1.6 kilometres vertically below the surface for DMLZ, a specific underground location. That figure does not describe every Grasberg working, so do not apply it to the whole district.
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| Feature | Historical open pit | Grasberg Block Cave |
|---|---|---|
| Where ore is extracted | From the surface | Underground |
| Access method | Surface access to the open pit | Underground access; the method is not stated in the reviewed sources |
| Ore body | Grasberg ore body | Same Grasberg ore body, per Freeport-McMoRan |
| Depth reference | Not stated | About 1.6 km below the surface at DMLZ, per PT Freeport Indonesia’s virtual tour (undated) |
Current operations and the September 2025 incident
Freeport-McMoRan’s September 2025 operational update reports a wet-material incident at one production block in the Grasberg Block Cave on September 8, 2025. The company reported seven team members died. This is the most serious operational fact in the current record, and any article about the mine’s operations should include it with the date and attribution.
The reviewed sources do not establish the full operating status of the district as of October 8, 2026. Claims about a restart, production rate, or current safety arrangements should be checked against Freeport-McMoRan’s most recent filings before publication, and should not be inferred from the 2025 update alone.
How to read a mining headline
- Check the date of every reserve or valuation figure. The technical report’s effective date and the year-end 2024 reserve date are different.
- Look for the price assumptions. A reserve estimated at $1,600 per ounce of gold and $3.25 per pound of copper is not a valuation at today’s prices.
- Separate reserves from value. Tonnage and metal quantities are not market value.
- Check whether a “largest” claim refers to gold only or to copper-gold, and who made it and when.
- Confirm which part of the district is meant. Surface, open pit, and underground block cave describe different workings with different depths.
- Attribute the $40 billion figure to its origin. It is a historical claim from secondary accounts, not a current appraisal.
Grasberg matters to readers for its scale and for the way a dated reserve figure can become a present-tense valuation in headlines. Keeping the date, the assumptions, and the attribution attached to each number is the simplest way to avoid repeating a claim the evidence does not support.
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