The ads tell us they're the ultimate symbol of love, the most perfect of stones, formed in the earth's core over millions of years.
That kind of mystique has created a $50 billion industry. But Mother Nature may be losing her patent on diamonds.
In a warehouse in Florida, and another one near Boston, real diamonds are being made in labs. The technique still hasn't been perfected, but it's a big step.
And what used to take thousands of years to create can now happen in a matter of days, and at a fraction of the price. Correspondent Vicki Mabrey reports.
Carter Clarke calls a 30,000-square-foot factory in Sarasota, Fla., his own personal diamond mine.
"This is the only American mine that grows diamonds that are of a nature that they can be used for jewelry," says Clarke. "We grow them in this machine."
Rough diamonds typically come out of the ground -- formed over millions of years, more than 100 miles below the earth's surface.
Clarke's machines replicate what happens under the earth, but they do it much quicker. In just three days, his machines can produce a diamond -- not cubic zirconia, not cut glass, but real diamonds.
"The pressure that goes inside this machine is hydraulic pressure," says Clarke. "And the carbon comes down and deposits atom by atom on the seed, and it grows and we end up with a diamond."
But there's a hitch. These diamonds are yellow, and that's because the nitrogen he needs to grow the stones quickly also adds color.
But where most people just see yellow, businessmen like Clarke see pure gold. Why? Because colored diamonds, which are more rare in nature than classic colorless ones, are more expensive.
And they are now fast on their way to becoming the girl's newest "best friend." Today, everywhere you look, on the red carpet, in windows of the most exclusive jewelry stores, the gems everyone's dying for are colored diamonds.
And it's a trend that Clarke is hoping to capitalize on by selling his man-made diamonds at about a quarter of the price of naturals.
"If you took the same quality of diamond as I have here, and if that were a natural diamond, that would be terrifically expensive," says Clarke. "A natural diamond of that size and that color and that cut and that quality would be somewhere in the neighborhood of $16,000 to $20,000. We will be selling that somewhere in the neighborhood of $3,500 to $4,000."
Until recently, Clarke knew nothing about diamonds. A retired brigadier general and entrepreneur, Clarke was looking for business opportunities in Russia, when scientists showed him blueprints for something they had developed for the Soviet space program.
It was a diamond-making machine. Clarke bought one, and now, eight years later, he has 23 of them.
How does it work? Carter explains that a tiny piece of diamond is mixed with graphite and metal and placed inside the machine.
After only three days, a ceramic cube – called the growth chamber – is removed and cracked open. What's inside doesn't look like a diamond yet. The metal casing has to be dipped in an acid bath to reveal the stone inside.
"And then we cut and polish it, and look at that beautiful thing. That's what it looks like after it's cut and polished," says Clarke.
Clarke hopes to produce traditional clear diamonds one day, when he figures out how to speed up the process and get the cost down. But it could be years before he can do it.
His competition, however, may be one step ahead of him.
Scientist Bob Linares runs a small secretive start-up company called Apollo, whose exact location 60 Minutes II is not allowed to reveal. Linares recently received a patent for his method of manufacturing diamonds, using hydrogen and methane gas.
His plan is to create diamonds that can be used – not only for jewelry, but also as semi-conductors for computing. For now, he is producing very pure, nearly colorless gemstones which have been called "too perfect to be natural."
"It is because we can program the computer to make these more perfect," says Linares. "In a batch of diamonds, every one will be identical."
What is the difference between this and a stone that was grown in the earth?
"There is no difference. A diamond is pure carbon," says Clarke. "This is pure carbon. A natural diamond is pure carbon -- all the same characteristics, all the same features, all the same chemical composition, so it's a diamond. A diamond is a diamond."
But Jerry Ehrenwald, president of the International Gemological Institute, one of the largest diamond-grading labs in the country, says man-made stones don't hold a candle to what nature creates.
"They are real synthetic diamonds. They're cooked. They're heated. They're put under pressure. They're made by man," says Ehrenwald.
"And when one considers a diamond, there's two points. There's the scientific end of it, and then there's the emotional end of it. … Will a person be as happy with something that's made in a laboratory as opposed to something that took so long to come to us as a gift of nature?"
That's what the jewelers 60 Minutes II talked with told us when we took Apollo and Gemesis stones on a test run through New York's famed Diamond District.
"It can sound like the real thing. It can look like the real thing, but they're ain't nothing like the real thing," says jeweler Phillip Weisner.
More than 100 million diamonds are sold in the U.S. every year, and no one benefits from that more than De Beers, the London-based cartel that has monopolized the diamond trade for more than a century.
De Beers says man-made diamonds aren't a threat, but they're investing millions of dollars to be able to detect them when they come out on the market. Lab-grown stones are virtually indistinguishable from those mined from the earth.
60 Minutes II asked David Weinstein at the International Gemological Institute to test some man-made stones.
Since man-made diamonds are real diamonds, they pass Weinstein's test with flying colors. But that test is the only weapon the average retail jeweler is going to have -- so with that test alone, they still won't be able to tell when a diamond is lab-grown.
That's why De Beers has developed sophisticated equipment that detects man-made diamonds. Using ultraviolet light, the machine shows how long it took the diamond to grow -- whether millions of years or just a couple of days.
But Clarke isn't trying to fool anyone with his Gemesis stones. He's lasering the company name right on each diamond, and is convinced that, at a quarter of the price of natural diamonds, the demand for them will be huge.
"If you give a woman a choice between a two-karat Gemesis stone and a half- or one-karat natural diamond, which do you think she'll go for," Mabrey asks Clarke.
"Now, come on. What would you answer to that? That's a pretty simple answer," says Clarke, who believes that bigger is better. "I don't think there's any such thing as a diamond too big."