This article has been adapted from our sister site across the pond, Fool UK.

Shareholders of Rio Tinto (NYSE: RIO) must be feeling a warm glow today, after the mining firm released its full-year results for 2010.

Rio's owners get splashed with cash
Rio's results were packed with positive news for its shareholders, which range from private investors of modest means to the world's largest pension funds.

As you'd expect, Rio -- a world-leading producer of aluminium, copper, and iron ore -- profited enormously from strongly rising commodity prices in 2010. For example, the price of copper rose 30% in 2010 and, last week, went over $10,000 per metric tonne for the first time. Similarly, the price of iron ore rose by 50% last year.

Thus, the Anglo-Australian miner almost tripled its net earnings to $14.3 billion in 2010, from $4.9 billion in 2009. However, Rio's second-half profit of $8.2 billion came in slightly below analyst expectations, but well ahead of the $3.7 billion recorded in the same period of 2009.

Rio's strong cash flow enabled it to reward its owners with a 140% increase in its full-dividend to 108 U.S. cents per share. In 2009, when Rio didn't pay an interim dividend, the dividend was a mere 45 cents.

As the icing on the cake, the world's third-largest miner announced that it would buy back $5 billion of its shares by the end of 2012. Although Rio's owners were expecting some form of buyback, this announcement arrived six months ahead of schedule.

No Rio carnival
With results as good as these, you might expect to see dancing in the streets of Rio's headquarters in Melbourne, Victoria.

However, investors may have been a little disappointed with the size -- and the two-year timescale -- of the share buyback, which amounts to just a thirtieth (3.3%) of Rio's $150 billion market value. Hence, as I write, Rio's shares are.

What next for Rio?
A string of mega-mergers and acquisitions (including buying Alcan at the top of the market in 2007) caused Rio's debt to soar to nearly $40 billion. At the end of 2010, this had plunged to a mere $4.3 billion, allowing an almost-ungeared Rio to be generous to its shareholders.

Despite being in such rude health, Rio will not be heading down the mega-M&A highway just yet. CEO Tom Albanese today said that Rio will only consider acquisitions with values under $5 billion, which is a mere morsel for the mega-miner.

Obviously, Rio is a bet on two things: the future direction of commodity prices and future growth from its clients in emerging markets and the BRIC (Brazil, Russia, India, China) economies.

Therefore, if you're bullish that price rises will continue for base metals, thermal coal, diamonds and so on, Rio is a solid bet. Conversely, if you feel that emerging markets and commodities are experiencing another bubble, Rio is not for you.

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Cliff D'Arcy doesn't own shares of any company mentioned. The Motley Fool has a disclosure policy.