The big mining companies do a terrific job of scouring the earth for everything from alumina to zinc. But lately they've become equally good at involving themselves in geopolitical skirmishes, either with their own governments or those of other countries, or otherwise keeping their names at the forefront of the news.

As you probably can guess, I'm referring primarily to the likes of Rio Tinto (NYSE:RTP), BHP Billiton (NYSE:BHP), and Vale (NYSE:VALE). The trio that controls the majority of the world's iron ore supply was in especially fine fettle during the second half of last week, when they all managed to make headlines in one form or another.

Has Hugo Chavez moved?
Take Vale, for instance. The company has announced a $5.6 billion spate of investments, obviously under pressure from Brazil's President Luiz Inacio Lula da Silva. He has been chagrinned by layoffs at Vale, and a cut in its capital expenditures in the face of the world's economic slowdown. Lula da Silva has maintained that Vale management has not taken the interests of the country's steel industry sufficiently to heart.

The investments still must pass a Vale board vote. Should they receive that imprimatur, they'll likely increase the production at the Vargem Grande, Conceicao Itabiritos, and Apolo mines in the state of Minas Gerais, adding thousands of jobs in the process.

There are still rumors circulating in Brazil that Lula da Silva is after the hide -- and the job -- of Vale CEO Roger Agnelli. But removing Agnelli wouldn't be a piece of cake, even for the country's president. Indeed, Brazil's bank Bradesco (NYSE:BBD) has a major stake in the company, and so any sort of heavy ax wielding would likely require the approval of that institution. For that reason, Vale is not as firmly under the president's thumb as is, for instance, state-run oil company Petrobras (NYSE:PBR).

Where all this is going is anyone's guess, but as I've said before, Brazil just might be taking on a tinge of Venezuela.

Forecasts on the rise
Beyond that, Rio Tinto ended the week by upping its iron ore production forecasts for this year. Rather than the prior 200 million metric tons, the company now expects to produce 210 million to 215 million metric tons. The impetus for the increase was third-quarter demand, which climbed 12% year over year and 5% from the prior quarter.

It appears that the demand improvement was spread across most of Asia, Europe, and North America. At the same time, the China Iron and Steel Association, which represents most of the major Chinese steelmakers, has suggested the establishment of a China-specific iron ore price, an idea that Rio Tinto has criticized roundly.

Despite that, Rio's aluminum group continues to struggle, with its production down 4% from a year ago. But that hasn't stopped U.S. aluminum producers Alcoa (NYSE:AA) and Kaiser Aluminum (NASDAQ:KALU) from watching their share prices more than double since March.

Partnership plunge
Rio Tinto and BHP pulled the plug on plans to jointly market 15% of the production from their planned iron ore joint venture in the Pilbara region of Australia. The venture itself has not yet received regulatory approval, and scuttling the idea of cooperating on the marketing of even a small portion of its output is seen as bowing to those customers or regulators who might attempt to block the deal.

BHP muscles in
And finally, as if Friday hadn't already been wild enough, BHP Billiton announced a bid of 204 million Australian dollars ($188 million) for a much smaller Australian mining company, United Minerals Corp. United Minerals also produces iron ore in the Pilbara region. The BHP bid requires that United Minerals drop a previously initiated deal with China Railway Materials Commercial Corp. Group for an 11.4% stake in the company. While China continues to make advances into Australia, the Aussies are increasing their resistance.

My take from all this is fairly simple: China continues to increase its thirst for minerals, metals, and other resources. That trend is likely to continue in the near term and ultimately the rest of the world will join in. As such, I'm convinced that Rio, BHP, and Vale remain sensible places for my Foolish friends to let their funds flourish for now.

Fool contributor David Lee Smith doesn't have financial interests in any of the companies mentioned. He does welcome your questions or comments. Petrobras is a recommendation of Income Investor. The Fool has a disclosure policy.