Maybe it's just the force of habit, but I'll often close out a column on focused natural resources companies by suggesting that investors "could just buy Rio Tinto (NYSE:RTP) or BHP Billiton (NYSE:BHP)." After all, it can be tricky to navigate the ups and downs of specific commodity cycles, but buying either of these stocks gives you broad exposure to the whole group.

While that's true, it may seem like I'm not giving BHP Billiton its proper due -- that I'm treating it like a commodity exchange-traded fund (ETF). While BHP does have operations in numerous commodity types, it's still a strong and well-run company in its own right.

Sales were up nearly 20% in the first half of the company's fiscal year, with underlying EBITDA climbing 42% and EBIT up 43%. Major EBIT contributors included petroleum (up 13.5% despite lower production), base metals (up 82%, largely on strong copper), and carbon steel (up nearly 130%). While stainless steel also posted EBIT growth (up 11%), aluminum was down on higher production costs, and the diamonds-and-specialty-products and coal categories were both down on lower realized prices and higher costs.

BHP's results are typical for the sector in two other ways. First, the company has new development projects starting left and right all over the world. Second, higher prices are translating into higher cash flow, and the company is sharing that with investors through higher dividends and share buybacks.

As you might expect in the midst of a bull run in commodities, BHP shares are trading at the lower end of the historical range -- perhaps suggesting that many investors don't expect the run to last indefinitely. What's more, there's talk of lower prices in many metal and commodity niches. That doesn't suggest that another huge run in the stock is too likely (it has nearly quadrupled from late 2002), but investors with faith in a more prolonged cycle might still see value here.

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Fool contributor Stephen Simpson has no financial interest in any stocks mentioned (that means he's neither long nor short the shares).