Maybe it's time to swap out The Motley Fool's traditional cap and bells with a miner's headlamp. After all, we have spent a lot of time lately talking about coal, oil, and the commodities market in general. With strong earnings from mining equipment company Joy Global (NASDAQ:JOYG), it's time to add one more to the list.

Earnings for the first quarter were exceptionally strong. Sales were up 35%, operating margins expanded considerably, and net earnings grew to more than $22 million (from less than $1 million a year ago).

Orders increased 44% in the quarter to $538 million, and new equipment orders rose 71% to roughly $250 million. At this point, nearly all of the company's 2005 production capacity is committed. While sales of new equipment grew 45%, they still made up only 31% of total sales, with the rest consisting of aftermarket goods and services.

It's not hard to pinpoint the reason for Joy's growth. Now that high coal prices are dropping cash into the hands of customers such as Peabody Energy (NYSE:BTU), Arch Coal (NYSE:ACI), and BHP Billiton (NYSE:BHP), they can at last buy that new machinery they've been wanting. Given a nearly seven-year slide in machinery spending dating back to 1997, there is certainly pent-up demand as coal companies had to postpone new equipment purchases.

Although coal has historically accounted for about 70% of Joy's business, there are additional growth possibilities. Joy has a solid footing in copper mining, and demand for machinery in iron mining, gold mining, and oil sands harvesting is also picking up. What's more, global sales might become increasingly important as China is attempting to significantly expand its coal production and other countries such as Russia and India are looking to expand their mining activities as well.

Investors should also realize that aftermarket sales are critically important to this company. Over the life of a mining machine, the owner may spend upwards of four times the original cost in aftermarket parts and services. Accordingly, strong growth in new equipment now should pave the way for ongoing aftermarket sales in the years to come.

Of course, nothing lasts forever, and this boom in mining capital expenditures will come to an end. Judging by the guidance provided by coal and steel companies, this cycle is expected to peak somewhere around 2006-2007, and since the lead-times for capital equipment are a bit longer, Joy should see its cyclical peak sometime around 2008.

As part of Wall Street's coal craze, these shares have been bid up considerably. Even with stellar growth, the shares trade at 36 times trailing earnings and more than 50 times trailing EV-to-FCF. That said, the company is projecting earnings to nearly triple for 2005, and the company looks to have an extremely solid book of business for at least the next two years. Although the easy money has no doubt already been made, these shares still might be able to provide some joy for its shareholders.

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Fool contributor Stephen Simpson, CFA, has no ownership interest in any stocks mentioned.