Grasberg sounds like a bucolic little town with picket fences and tire swings nestled into the great heartland of America. Nope, it's a giant gold and copper mine complex in Indonesia. And if you're an investor interested in the precious metals or industrial metals industries, you'll want to know a lot more about the Grasberg mine. It's a top global producer, has 24 years to run if current production trends hold, and it's so troubled that Rio Tinto plc (NYSE:RIO) is thinking about walking away from its partnership there with Freeport-McMoRan Inc (NYSE:FCX).

How big is big?

Grasberg is a collection of operating mines and mine projects in "The remote highlands of the Sudirman Mountain Range in the province of Papua, Indonesia, which is on the western half of the island of New Guinea." Don't pull out a map, just know that it's on the other side of the world near China, a key global commodities customer, and Australia. It was discovered in 1988.

An image of Freeport-McMoRan employees working.

Image source: Freeport-McMoRan   

The really important story, however, is all about size. By Freeport-McMoRan's estimates Grasberg holds 25.8 million ounces of gold and 26.9 billion pounds of copper... The means that Grasberg has the largest gold reserves in the world and the third largest copper reserves. To add some perspective, Northern Dynasty Minerals Ltd (NYSEMKT:NAK), which is trying to develop the giant Pebble project in Alaska, notes that Pebble's gold reserves are equal to 1.9% of the gold ever produced in the world. Grasberg is bigger!  

Currently the complex has three operating mines. The Grasberg open pit mine started operations in 1990 and is expected to produce through 2017. The DOZ underground mine was worked between 1989 and 1991, and was then reopened in 2000. It's expected to continue producing through 2020. And the Big Gossan underground mine started up in 2010 and is expected to hit full production next year. In addition to these currently operating mines, there are development projects in the works, as well. For example, Rio Tinto expects the Grasberg underground block cave project to come online at about the same time that the Grasberg open pit mine winds down.

A bar chart showing that Grasberg mine complex has the largest gold reserves in the world.

Pebble is big, Grasberg is bigger!  Image source: Northern Dynasty Minerals Ltd  

To sum all of that up, the Grasberg mine complex is big, strategically located near a key customer, and it's going to be producing for a long time. You'd think partners Freeport-McMoRan and Rio Tinto would be ecstatic to have stakes in this property. You would be wrong. In fact, Rio Tinto is reportedly thinking about walking away from its stake in Grasberg.

Jumping ship

The big problem right now is the Indonesian government's decision to enact new rules that have, effectively, halted copper exports from Grasberg. It's really a pretty complex political mess and Freeport-McMoRan is negotiating with the Indonesian government to come to a resolution that, "would be in the best interests of all stakeholders." (Work stoppages have also been something of an ongoing problem, with a current stoppage at a copper smelter adding to the mine's woes right now.)

It's so bad that Rio Tinto CEO Jean-Sebastian Jacques recently commented at an analyst briefing that, "Everyone was taken by surprise." And, "There is no doubt that Grasberg is a world-class resource. But the key question, especially in the light of what happened three weeks ago, is: is Grasberg a world-class business for us?"  

The problem for Rio Tinto is that it currently only gets 40% of production over set production amounts. And, reportedly, that's meant that the global mining giant hasn't gotten anything from the mine since 2014. It might see some metal this year, but only if an agreement with the Indonesian government can be reached.  

Its take is set to increase to 40% of all production in 2021, but that's still a few years away and the current issues are troubling, to say the least. Worse, according to Rio Tinto CEO Jacques, "If we want to have a meaningful offtake and stream beyond 2021, we would need to invest in a big way in the coming years." Why invest meaningful sums of money into a troubled mining operation?

An image listing the current troubles between Indonesia and the Grasberg mine.

A quick primer on what's going on at Grasberg...  Image source: Freeport-McMoRan Inc   

Freeport-McMoRan's not as lucky as more diversified Rio Tinto, which focuses heavily on iron ore. Grasberg represents 31% of Freeport's copper reserves and 95% of its gold reserves. Freeport simply doesn't have the luxury of walking away without taking a huge hit. Which means the Indonesian government could have the upper hand in the negotiations to solve the current issue.  

A mine to watch

Because of its size, the events occurring at the Grasberg mine complex could have a notable impact on global supply and demand. So, if you are interested in gold or copper, you should keep an eye on what's going down in Indonesia even if you've never heard of Grasberg. And if you are a Freeport-McMoRan or Rio Tinto investor you'll want to pay particular attention. Indeed, Grasberg is dealing with tense political issues that may have turned one of the world's biggest gold and copper mines into a serious liability.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.