Money is a funny thing. It plays such a big role in our lives that we rarely stop to think that the cash we strive to accumulate has almost no inherent worth.

Of course, for the world's financial systems to function, it's better not to dwell on that truth. Once society has decided to honor cowrie shells or tulip bulbs or big rocks as a way to pay debts and acquire goods, we all have to play along. You can't have people looking in their wallets and saying, "Hey, these pictures of dead presidents are just heavy-duty paper. I'm not accepting these crummy things for work anymore--and certainly not so few of them."

But there is one store of value that has been treasured by nearly every society that has encountered it. One element that has for millennia captivated humans with its glitter and glow. One treasure--whose luster is buffed by the knowledge of how hard it is to pry from the earth--that quickens the pulse of young women and old men alike. Nothing else is as good as gold. Gold has a combination of physical properties that seem to make it irresistible to humans. Among its most significant properties:

• It's immutable. That gold that forms a circle on your finger today could have been mined in Spain before Christ was born, fashioned into a heavy torque necklace by Celts in the 4th century, buried in a bog for hundreds of years, rediscovered, traded, melted down to form Venetian ducats in the 15th century, and shipped to China as payment for silks and spices. Or it could have been blasted out of the earth just a few years ago. Gold does not rust or corrode. In fact, pure gold won't even tarnish. Precious artworks made by the ancient Egyptians are as beautiful today as they were when they were received by the pharaohs.

• It's malleable. A single ounce of gold can be stretched into a thin wire five miles long or hammered into a 100-square-foot sheet. Because it's soft, it's easy to work with. That means that ancient cultures without sophisticated tools could fashion elaborate works of art.

• It's scarce. You know how people are. When anything becomes common, we just don't value it as much. After trade with the Far East got far easier, those precious...

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