Yeah, yeah . most of us have heard how gold has been surging, having more than doubled over the last five years. But take a look at the price of copper: In just the past six months or so, it has gone from around $2.20 per pound to $3.40, up more than 50%. In the past year, it's doubled. Over the past five years, it's up nearly five-fold, from less than $0.75 per pound.

If you were wondering why those simple copper pipes and fixtures you see at Home Depot (NYSE:HD) and Lowe's (NYSE:LOW) suddenly seem kind of pricey, that's why. Driving the price increases have been factors such as a lasting construction boom -- copper is used in plumbing, wires, heating devices, and air conditioners -- both in America and abroad (especially in developing countries, such as China). That represents rising demand.

Meanwhile, supply has been tight. Researchers have suggested that there isn't enough copper available to be mined to serve the needs of everyone on the planet. Making matters worse, supply-wise, has been a strike at a major Chilean copper mine. (Don't panic, though -- there are some alternatives to copper, such as newfangled flexible plastic water piping.)

As Daniel Gross pointed out in a article last year, copper is used in cars and electronics. A typical car might contain 50 pounds of it, while a typical cell phone is composed of roughly 19% copper. Indeed, it's the world's No. 3 most-used metal, after iron and aluminum.

So -- should you invest in it? The answer (as with any investment) is only if you know what you're doing. Just because it has quintupled in a few years doesn't mean it will do so again. It may even fall in value.

Guard that A/C!
Even if you choose not to invest in copper, you shouldn't ignore this story. Why? Because news stories are popping up about a new kind of crime sweeping the nation: the theft of copper from homes, companies and worksites. A recent Orlando Sentinel article noted that "the city of Orlando alone has seen 142 cases of copper theft and 51 cases of aluminum theft so far this year. That's twice as many as in the same period last year." Here in The Motley Fool's discussion board community, a member recently shared a story about a major break-in and copper theft at his home.

Why are thieves so interested? Well, it seems that an average home's air conditioning unit contains about 50 pounds of copper pipes. With scrap metal yards paying around $3 per pound, that's $150 sitting outside your house. And when it comes to commercial air-conditioning units . well, as you can imagine, the value is much higher.

Keep learning
Read more on copper in these articles:

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Longtime Fool contributor Selena Maranjian owns shares of Home Depot. The Fool's disclosure policy has gone solid gold.