The plot just might be thickening at London-based mining giant Rio Tinto (NYSE:RTP). Sure, Australian rival BHP Billiton (NYSE:BHP) has been chasing it for months. And sure, Alcoa (NYSE:AA) and Aluminum Corp. of China (NYSE:ACH) combined for a stake in the big metals producer earlier this year. But it now appears that there might -- just might -- be another potential player beginning to circle the company.

According to the rumor mill, ArcelorMittal (NYSE:MT), headed up by billionaire industrialist and newly minted member of the board of Goldman Sachs Lakshmi Mittal, may be interested in entering the chase.

BHP Billiton, the world's largest mining company, has been after Rio Tinto since late last year. Its latest offer would involve the exchange of 3.4 of its shares for each of Rio's outstanding shares. The latter has, however, continuously stiff-armed its pursuer.

The two companies made news last week when a new iron ore pricing agreement was reached with China's biggest steelmaker, Baosteel Group, that would result in an increase in the price of iron ore by about 85%. Iron ore, which accounts for about 30% of Rio Tinto's earnings, is a key ingredient in the manufacture of steel.

Whether Mittal will formally enter the pursuit of Rio Tinto and make things even more interesting is open to question. What isn't in doubt is the increasing importance of and interest in the big mining companies. And with the world's appetite for all manner of metals and other resources continuing to escalate, it's hard to imagine how attention to the group can wane for years to come.

On that basis alone, I'd strongly recommend that my Foolish friends consider further digging into the likes of Rio, BHP, Brazil's Vale (NYSE:RIO), or U.S.-based copper, molybdenum, and gold producer Freeport-McMoRan (NYSE:FCX).

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