Coal may be "just" another commodity, but there's no denying the strength of this market right now. And as the largest private-sector coal company in the world, Peabody Energy (NYSE:BTU) is certainly enjoying this boom.

Honestly, if you've followed coal companies much over the past year, this will all look really familiar. Revenue was up 22% as the company sold about 4% more tons of coal, but once again saw double-digit price increases for that black gold. And while operating costs are rising, the company is staying well ahead of them. Operating profit more than doubled, and EBITDA was up about 56% for the period.

Given the ongoing tightness in the market, Peabody laid in some additional contracts at prices that are very attractive on a historical basis. That said, there might be some wondering why Peabody is leaving tons of coal unpriced and uncontracted. I believe the reason is twofold.

First, it's generally a good idea to leave yourself a little bit to sell on the spot market in case one of your customers finds itself hard up for coal (which happened to Wheeling Pittsburgh Steel (NASDAQ:WSPC) recently). Second, it gives you the potential to sell that coal at possibly even higher spot rates, and it also gives you a little leeway in case you have some production difficulties.

Whether or not you think coal stocks like Peabody are really cheap today depends on your long-term outlook for coal prices. I'd say the demand side of the picture is pretty well locked-in -- utilities have low inventories, and there are increasing numbers of new coal power plant projects on the books. So even if we see an economic slowdown, there's likely to be pretty decent demand from utilities.

And let's not forget the potential that coal technologies will increasingly be used as a substitute for natural gas and/or oil. Even at today's higher coal prices, coal is still a lot cheaper than gas and oil on an energy-content basis.

Having duly learned my lesson about listening to analyst projections of future commodity prices with copper and Phelps Dodge (NYSE:PD), I'm not about to say that the coal boom is over or peaking. Instead, I'll say that Peabody remains a fine company, but investors new to the space might also want to check out Massey (NYSE:MEE), Foundation (NYSE:FCL), and CONSOL (NYSE:CNX) before casting their lots with a single coal stock.

Dig deeper for more Foolish thoughts on coal:

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