It might take less time to develop a major minerals mine than to acquire a major minerals company. Nevertheless, the acquisition of Rio Tinto (NYSE:RTP) by BHP Billiton (NYSE:BHP) could be inching closer, due to a newly issued blessing of the combination by the Australian Competition and Consumer Commission.

A combination of BHP and Rio Tinto would, along with Brazil's Vale (NYSE:RIO), control a major share of the world's iron ore. The Australian commission's finding that a combination of the two big miners would "not be likely to substantially lessen competition," follows an earlier approval by U.S. authorities. The second imprimatur leaves only a European commission to weigh in, which it will do by Jan. 15, 2009. In rendering his organization's decision, ACCC Chairman Graeme Samuel noted that, "The merged firm would be a significant global supplier of a range of commodities, including iron ore, coal, bauxite, alumina, copper and uranium."

Since early this year, BHP has had an offer of 3.4 of its shares for each Rio Tinto share on the table. It's an offer that Rio Tinto management has spurned, claiming it undervalues their company. It's also an offer that's been objected to by customers of the two companies -- including Chinese metals interests. Largely based on concerns in its government and its nation's steel industry, Aluminum Corp. of China (NYSE:ACH) -- or Chinalco -- teamed up with Alcoa (NYSE:AA) earlier this year to buy a stake in Rio Tinto.

Despite Rio Tinto's opposition to the offer, the eventual likelihood of a deal is increasing with the slide in the target company's shares that has led to a doubling of the effective premium being offered by BHP in just the past month. It was nearly 18 months ago that I first broached the subject of a merger between the two mining behemoths. And while the combination won't occur until well into next year -- if at all -- BHP's obvious patience makes me willing to bet a little more each day that the long-running courtship will lead to an eventual marriage.

Given the slide in Rio Tinto's shares, Fools with a taste for natural resources might consider joining me in my wager.

BHP and Rio Tinto each are four-star companies -- out of five -- in ratings by Motley Fool CAPS players. Why not add your opinion on one or both?

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Fool contributor David Lee Smith doesn't own shares in any of the companies mentioned. He does, however, welcome your questions, comments, or kibitzing. The Fool has a disclosure policy.