I am sitting in a fast-food restaurant outside Boston that, because of a nondisclosure agreement I had to sign, I am not allowed to name. I'm waiting to visit Apollo Diamond, a company about as secretive as a Soviet-era spy agency. Its address isn't published. The public relations staff wouldn't give me directions. Instead, an Apollo representative picks me up at this exurban strip mall and drives me in her black luxury car whose make I am not allowed to name along roads that I am not allowed to describe as twisty, not that they necessarily were.

"This is a virtual diamond mine," says Apollo CEO Bryant Linares when I arrive at the company's secret location, where diamonds are made. "If we were in Africa, we'd have barbed wire, security guards and watch towers. We can't do that in Massachusetts." Apollo's directors worry about theft, corporate spies and their own safety. When Linares was at a diamond conference a few years ago, he says, a man he declines to describe slipped behind him as he was walking out of a hotel meeting room and said someone from a natural diamond company just might put a bullet in his head. "It was a scary moment," Linares recalls.

Bryant's father, Robert Linares, working with a collaborator who became a co-founder of Apollo, invented the company's diamond-growing technique. Robert escorts me into one of the company's production rooms, a long hall filled with four refrigerator-size chambers bristling with tubes and gauges. As technicians walk past in scrubs and lab coats, I glance inside the porthole window of one of the machines. A kryptonite-green cloud fills the top of the chamber; at the bottom are 16 button-size disks, each one glowing a hazy pink. "Doesn't look like anything, right?" Robert says. "But they will be half-caraters in a few weeks."

In 1796, chemist Smithson Tennant discovered that diamond is made out of carbon. But only since the 1950s have scientists managed to produce diamonds, forging them out of graphite subjected to temperatures as high as 2,550 degrees Fahrenheit and pressures 55,000 times greater than that of earth's atmosphere. But the stones were small and impure. Only the grit was useful, mostly for industrial applications such as dental drills and hacksaw blades. Over the past decade, however, researchers such as Linares have perfected a chemical process that grows diamonds as pure and nearly as big as the finest specimens hauled out of the ground. The process, chemical vapor deposition (CVD), passes a carbon gas cloud over diamond seeds in a vacuum chamber heated to more than 1,800 degrees. A diamond grows as carbon crystallizes on top of the seed.

Robert Linares has been at the forefront of crystal synthesis research since he started working at Bell Labs in Murray Hill, New Jersey, in 1958. He went on to start a semiconductor company, Spectrum Technologies, which he later sold, using the proceeds to bankroll further research on diamonds. In 1996, after nearly a decade working in the garage of his Boston home—no kidding, in the garage, where he'd set up equipment he declines to describe—he discovered the precise mixture of gases and temperatures that allowed him to create large single-crystal diamonds, the kind that are cut into gemstones. "It was quite a thrill," he says. "Like looking into a diamond mine."

Seeking an unbiased assessment of the quality of these laboratory diamonds, I asked Bryant Linares to let me borrow an Apollo stone. The next day, I place the .38 carat, princess-cut stone in front of Virgil Ghita in Ghita's narrow jewelry store in downtown Boston. With a pair of tweezers, he brings the diamond up to his right eye and studies it with a jeweler's loupe, slowly turning the gem in the mote-filled afternoon sun. "Nice stone, excellent color. I don't see any imperfections," he says. "Where did you get it?"

"It was grown in a lab about 20 miles from here," I reply.

He lowers the loupe and looks at me for a moment. Then he studies the stone again, pursing his brow. He sighs. "There's no way to tell that it's lab-created."

More than one billion years ago, and at least 100 miles below the surface of the earth, a mix of tremendous heat and titanic pressure forged carbon into the diamonds that are mined today. The stones were brought toward the surface of the earth by ancient underground volcanoes. Each volcano left a carrot-shaped pipe of rock called kimberlite, which is studded with diamonds, garnets and other gems. The last known eruption of kimberlite to the surface of the earth happened 47 million years ago.

Diamonds have been extracted from almost every region of the world, from north of the Arctic Circle to the tropics of western Australia. Most diamond mines start with a wide pit; if the kimberlite pipe has a lot of diamonds, miners dig shafts 3,000 feet or more deep. In areas where rivers once ran over kimberlite seams, people sift diamonds from gravel. Loose diamonds used to turn up in fields in the Midwest in the 1800s; they were deposited there by glaciers. Most geologists believe that new diamonds continue to form in the earth's mantle—much too deep for miners to reach.

The word "diamond" comes from the ancient Greek adamas, meaning invincible. People in India have mined diamond gems for well over 2,000 years, and first-century Romans used the stones to carve cameos. Over the ages, diamonds acquired a mystique as symbols of wealth and power. During the 16th century, the Koh-i-Noor, a 109-carat diamond from the Kollur mine in southern India, was perhaps the most prized item on the Indian subcontinent. Legend held that whoever owned it would rule the globe. "It is so precious," noted a writer at the time, "that a judge of diamonds valued it at half the daily expense of the whole world." Great Britain got the stone in 1849 when Lahore and Punjab became part of the British Empire; the diamond now sits in the Tower of London, the centerpiece of a crown made for Queen Elizabeth in 1937.

And yet diamonds are simply crystallized pure carbon, just as rock candy is crystallized sugar—an ordered array of atoms or molecules. Another form of pure carbon is graphite, but its atoms are held together in sheets rather than rigidly attached in a crystal, so the carbon sloughs off easily, say, at the tip of a pencil. Thanks to the strength of the bonds between its carbon atoms, diamond has exceptional physical properties. It's the hardest known material, of course, and it doesn't react chemically with other substances. Moreover, it's fully transparent to many wavelengths of light, is an excellent electrical insulator and semiconductor, and can be tweaked to hold an electrical charge.

It's because of these admittedly unglamorous properties that lab-produced diamonds have the potential to dramatically change technology, perhaps becoming as significant as steel or silicon in electronics and computing. The stones are already being used in loudspeakers (their stiffness makes for an excellent tweeter), cosmetic skin exfoliants (tiny diamond grains act as very sharp scalpels) and in high-end cutting tools for granite and marble (a diamond can cut any other substance). With a cheap, ready supply of diamonds, engineers hope to make everything from higher-powered lasers to more durable power grids. They foresee razor-thin computers, wristwatch-size cellphones and digital recording devices that would let you hold thousands of movies in the palm of your hand. "People associate the word diamond with something singular, a stone or a gem," says Jim Davidson, an electrical engineering professor at Vanderbilt University in Tennessee. "But the real utility is going to be the fact that you can deposit diamond as a layer, making possible mass production and having implications for every technology in electronics."

At the U.S. Naval Research Lab, a heavily guarded compound just south of the U.S. Capitol, James Butler leads the CVD program. He wears a gold pinky ring that sparkles with one white, one green and one red diamond gemstone, all of them either created or modified in a lab. "The technology is now at a point that we can grow a more perfect diamond than we can find in nature," he says.

Butler, a chemist, pulls from his desk a metal box that brims with diamonds. Some are small, square and yellowish; others are round and transparent disks. He removes one wafer the size of a tea saucer. It's no thicker than a potato chip and sparkles under the fluorescent light. "That's solid diamond," he says. "You could use something like this as a window in a space shuttle."

The military is interested in lab-grown diamonds for a number of applications, only some of which Butler is willing to discuss, such as lasers and wearproof coatings. Because diamond itself doesn't react with other substances, scientists think it's ideal for a biological weapons detector, in which a tiny, electrically charged diamond plate would hold receptor molecules that recognize particular pathogens such as anthrax; when a pathogen binds to a receptor, a signal is triggered. Butler, working with University of Wisconsin chemist Robert Hamers, has produced a prototype of the sensor that can detect DNA or proteins.

The largest single-crystal diamond ever grown in a lab is about .7 inches by .2 inches by .2 inches, or 15 carats. The stone isn't under military guard or at a hidden location. It's in a room crowded with gauges and microscopes, along with the odd bicycle and congo drum, on a leafy campus surrounded by Washington, D.C.'s Rock Creek Park. Russell Hemley, director of the Carnegie Institution's Geophysical Lab, started working on growing diamonds with CVD in 1995. He pulls a diamond out of his khakis. It would be hard to mistake this diamond for anything sold at Tiffany. The rectangular stone looks like a thick piece of tinted glass.

Hemley and other scientists are using laboratory and natural diamonds to understand what happens to materials under very high pressure—the type of pressure at the center of the earth. He conducts experiments by squeezing materials in a "diamond anvil cell," essentially a powerful vise with diamonds at both tips.

A few years ago, Hemley created one of the hardest known diamonds. He grew it in the lab and then placed it in a high-pressure, high-temperature furnace that changed the diamond's atomic structure. The stone was so hard that it broke Hemley's hardness gauge, which was itself made out of diamond. Using the super-hard diamond anvil, Hemley has increased the amount of pressure he can exert on materials in his experiments up to four million to five million times greater than atmospheric pressure at sea level.

"Under extreme conditions, the behavior of materials is very different," he explains. "Pressure makes all materials undergo transformations. It makes gases into superconductors, makes novel super-hard materials. You can change the nature of elements."

He discovered, for instance, that under pressure, hydrogen gas merges with iron crystals. Hemley believes that hydrogen might make up a portion of the earth's core, which is otherwise composed largely of iron and nickel. He has been studying the hydrogen-iron substance to understand the temperature and composition of the center of our planet.

In another surprising discovery, Hemley found that two common bacteria, including the intestinal microorganism E. coli, can survive under colossal pressure. He and his colleagues placed the organisms in water and then ratcheted up the diamond anvil. The water solution soon turned into a dense form of ice. Nevertheless, about 1 percent of the bacteria survived, with some bacteria even skittering around. Hemley says the research is more evidence that life as we know it may be capable of existing on other planets within our solar system, such as under the crust of one of Jupiter's moons. "Can there be life in deep oceans in outer satellites like Europa?" asks Hemley. "I don't know, but we might want to be looking."

Hemley hopes to soon surpass his own record for the largest lab-grown diamond crystal. It's not clear who has produced the largest multiple-crystal diamond, but a company called Element Six can make wafers up to eight inches wide. The largest mined diamond, called the Cullinan diamond, was more than 3,000 carats—about 1.3 pounds—before being cut. The largest diamond so far found in the universe is the size of a small planet and located 50 light-years away in the constellation Centaurus. Astronomers with the Harvard-Smithsonian Center for Astrophysics discovered the gigantic stone a few years ago, and they believe the 2,500-mile-wide diamond once served as the heart of a star. It's ten billion trillion trillion carats. The astronomers named it Lucy in honor of the Beatles' song "Lucy in the Sky With Diamonds."

Natural diamonds aren't particularly rare. In 2006, more than 75,000 pounds were produced worldwide. A diamond is a precious commodity because everyone thinks it's a precious commodity, the geological equivalent of a bouquet of red roses, elegant and alluring, a symbol of romance, but ultimately pretty ordinary.

Credit for the modern cult of the diamond goes primarily to South Africa-based De Beers, the world's largest diamond producer. Before the 1940s, diamond rings were rarely given as engagement gifts. But De Beers' marketing campaigns established the idea that the gems are the supreme token of love and affection. Their "A Diamond Is Forever" slogan, first deployed in 1948, is considered one of the most successful advertising campaigns of all time. Through a near total control of supply, De Beers held almost complete power over the diamond market for decades, carefully hoarding the gemstones to keep prices—and profits—high. While the company has lost some of its power to competitors in Canada and Australia over the past few years, it still controls almost two-thirds of the world's rough diamonds.

Diamond growers are proud of the challenge they pose to De Beers and the rest of the natural diamond industry. Apollo's slogan is "A Diamond Is for Everyone." So far, though, Apollo's colorless gems cost about the same as natural stones, while the company's pink, blue, champagne, mocha and brown diamonds retail for about 15 percent less than natural stones with such colors, which are very rare and more expensive than white diamonds. Meanwhile, consumers may well be receptive to high-quality, laboratory-produced diamonds. Like most open-pit mines, diamond mines cause erosion, water pollution and habitat loss for wildlife. Even more troubling, African warlords have used diamond caches to buy arms and fund rebel movements, as dramatized in the 2006 movie Blood Diamond. Actor Terrence Howard wears a diamond lapel pin with Apollo stones. He told reporters, "Nobody was harmed in the process of making it."

Half a dozen other companies have begun to manufacture gem-quality diamonds using not CVD but a process that more closely mimics the way diamonds are created in the earth. The method—basically an improvement on how scientists have been making diamonds since the 1950s—requires heat of more than 2,000 degrees and pressure 50 times greater than that at the surface of the earth. (Both the heat and pressure are more than what CVD requires.) The washing machine-size devices can't produce stones much larger than six carats. These HPHT diamonds—the initials stand for high pressure and high temperature—have more nitrogen in them than CVD diamonds do; the nitrogen turns the diamonds amber-colored. For now, though, the process has a significant benefit over CVD: it's less expensive. While a natural, one-carat amber-colored diamond might retail for $20,000 or more, the Florida-based manufacturer Gemesis sells a one-carat stone for about $6,000. But no one, Gemesis included, wants to sell diamonds too cheaply lest the market for them collapse.

Gemologists plying everyday tools can seldom distinguish between natural and lab-grown diamonds. (Fake diamonds such as cubic zirconia are easy to spot.) De Beers sells two machines that detect either chemical or structural characteristics that sometimes vary between the two types of stones, but neither machine can tell the difference all the time. Another way to identify a lab-produced diamond is to cool the stone in liquid nitrogen and then fire a laser at it and examine how the light passes through the stone. But equipment is expensive and the process can take hours.

Diamonds from Apollo and Gemesis, the two largest manufacturers, are marked with a laser-inscribed insignia visible with a jeweler's loupe. Last year, the Gemological Institute of America, an industry research group, began to grade lab-grown stones according to carat, cut, color and clarity—just as it does for natural stones—and it provides a certificate for each gem that identifies it as lab grown.

The diamond-mining companies have been fighting back, arguing that all that glitters is not diamond. De Beers' ads and its Web sites insist that diamonds should be natural, unprocessed and millions of years old. "Diamonds are rare and special things with an inherent value that does not exist in factory-made synthetics," says spokeswoman Lynette Gould. "When people want to celebrate a unique relationship they want a unique diamond, not a three-day-old factory-made stone." (De Beers does have an investment in Element Six, the company that makes thin industrial diamonds.)

The Jewelers Vigilance Committee (JVC), a trade group, has been lobbying the Federal Trade Commission to prevent diamond manufacturers from calling their stones "cultured," a term used for most of the pearls sold today. (People in the mined diamond business use less-flattering terms such as "synthetic.") The JVC filed a petition with the agency in 2006, claiming that consumers are often confused by the nomenclature surrounding lab-grown diamonds.

From the beginning of his research with CVD more than 20 years ago, Robert Linares hoped that diamonds would become the future of electronics. At the heart of almost every electrical device is a semiconductor, which transmits electricity only under certain conditions. For the past 50 years, the devices have been made almost exclusively from silicon, a metal-like substance extracted from sand. It has two significant drawbacks, however: it is fragile and overheats. By contrast, diamond is rugged, doesn't break down at high temperatures, and its electrons can be made to carry a current with minimal interference. At the moment, the biggest obstacle to diamond's overtaking silicon is money. Silicon is one of the most common materials on earth and the infrastructure for producing silicon chips is well established.

Apollo has used profits from its gemstones to underwrite its foray into the $250 billion semiconductor industry. The company has a partnership Bryant Linares declines to confirm to produce semiconductors specialized for purposes he declines to discuss. But he revealed to me that Apollo is beginning to sell one-inch diamond wafers. "We anticipate that these initial wafers will be used for research and development purposes in our clients' product development efforts," Linares says.

Before I leave the Apollo lab, Robert and Bryant Linares take me into a warehouse-like room about the size of a high-school gym. It's empty, except for large electrical cables snaking along the floor. The space will soon be filled with 30 diamond-making machines, the men say, nearly doubling Apollo's production capacity. It will be the world's first diamond factory, they say. "There was a copper age and a steel age," Bryant says. "Next will be diamond."

Ulrich Boser is writing a book about the world's largest unsolved art heist.

Photographer Max Aguilera-Hellweg specializes in medical and scientific subjects.