There weren't too many people out there telling us to buy mining-equipment companies like Bucyrus (NASDAQ:BUCY) and Joy Global (NASDAQ:JOYG) back before the boom in metals prices and mining stocks. Now, though, there seem to be plenty telling us that the good times will soon pass.

For now at least, business is still booming for Bucyrus. Revenue was up 41% in the latest quarter, and growing margins helped operating income more than double. Sales of new machines grew by nearly 80%, aftermarket parts sales grew more than 30%, and the backlog rose by much more than 100% over last year's level.

So, this is as good as it gets, right? Well, I don't know about that. Bucyrus is a more diversified company than some may think. Coal miners, metals miners, and oil sands producers all have need of electric shovels and other heavy equipment. In the case of oil sands, for instance, this company has about half of the market for shovels, with Harnischfeger holding the rest. And if we listen to our friends up north, none of those oil-sands projects are slowing down.

What's more, it's important to remember that the mining industry generally under-invested in exploration and development over recent years because current spot prices at the time didn't make those activities economically attractive. Now, though, that's all changing. Peabody (NYSE:BTU) wants to dig up more coal. CVRD (NYSE:RIO) wants to dig up more iron. Alcoa (NYSE:AA) wants to dig up more bauxite. And Rio Tinto (NYSE:RTP) and BHPBilliton (NYSE:BHP) want to dig more of just about everything. And don't you think copper companies are looking at more projects now that the price of copper is so high?

It's certainly true that high materials costs could lead to an economic slowdown, which would in turn lead to lower demand (and lower prices) for those materials. That said, mineral exploration and production projects are multi-year commitments, and I don't think mining companies will suddenly cancel their orders en masse just because the economy gets a little lumpy. After all, in many cases, companies had been holding off new equipment purchases for years and now really need to refurbish and update their fleets.

I'm sanguine about the near-term future of the business here, but I'm not rushing to buy the stock. I like the fact that worries about basic materials companies have pushed this stock down more than 15% off its high, but the volatility seems like more trouble than it's worth. Energy and materials stocks have become trading playthings, and that sort of setup can create more stress for serious investors than the gains may be worth.

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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).