They are older than the dinosaurs, older than nearly everything else on earth. They have been used to cut glass, cure snakebites and charm kings and queens. Famed for their flashing beauty, diamonds are the hardest substances on earth and among the most useful.
A glittering gallery of diamonds opened this month at the American Museum of Natural History in New York City. On display are crowns and books studded with thousands of tiny gems. Larger stones twinkle inside glass cases. Models of mines lead visitors through the dangers and delights of diamond exploration.
"Diamonds help us understand the history of the earth," says geologist George Harlow, who organized the exhibition, the most complete diamond show ever. The show arrives at a time when scientists are developing exciting new uses for these sparkling stones.
Crystals From Inner Earth
Most diamonds were formed billions of years ago in an inner layer of the earth called the mantle. About 100 miles
underground, the mantle puts extreme heat (1,800°F) and pressure on carbon, the common black substance in coal and
pencils. These forces turn black carbon into clear diamond crystal. As the crystal grows, it may trap other chemicals inside, creating what Harlow calls "a space capsule from the
inner earth."
How did diamonds arrive on the earth's surface? They were shot forth in boiling eruptions of melted rock hundreds of millions of years after they were formed. These eruptions were smaller but much more powerful than those of modern volcanoes. "The most recent one occurred about 50 million years ago," says Harlow, "though there's no reason one couldn't happen now."
In 1872 scientists discovered that these ancient volcanoes acted like elevators, bringing diamonds from deep inside the earth up through rocky "pipes" to the surface. Miners began to dig where they found the telltale pipes, evidence of the long-ago eruptions.
But diamonds have also been found far from these places. They've been spotted in the sand and gravel in India since about 1,000 B.C. That's because volcanic rock eroded and washed away over time. Rivers and streams carried the diamonds far from the original volcanoes.
Today diamonds are mined on every continent except Europe and Antarctica. South Africa once shone as the diamond capital of the world. A huge rush there was sparked by a 15-year-old's lucky diamond find in a bed of gravel in the 1860s. Now Australia is the king of diamonds, producing 39% of the gems found each year. Thanks to new methods of finding gems, mines were opened just a few years ago in Canada and Colorado.
A Brilliant Business
Digging for diamonds is an expensive and exhausting operation. Miners may dig through about 250 tons of rock to find just one stone. And only a fraction of the 10 tons of natural diamonds
mined each year are perfect enough to be fashioned into necklaces, pins and rings.
The 80% of diamonds found each year that are too flawed, oddly shaped or small for jewels are still valuable. These stones, called industrial diamonds, are used to create thousands of products, from protective eyeglasses to computer chips.
Every day, workers cut, grind, scrape or shape runways, building materials and streets using diamonds' hard edges. Dentists drill through tooth enamel quickly with diamond-tipped tools, and doctors perform surgery with diamond-edged scalpels.
Most businesses no longer buy costly natural diamonds. They have switched to synthetic, or man-made, diamonds. In 1955 researchers at General Electric figured out how to imitate the conditions of heat and pressure that turn carbon into diamond. The discovery made diamonds cheaper and easier to shape for all kinds of purposes.
The Pioneer spacecraft went to Venus in 1978 with a tiny natural diamond window. Future missions may be equipped with synthetic diamond windows, which hold up well in space. Golf clubs, supercomputers, X-ray detectors and other things may all be improved by diamonds.
"Diamonds have made a large footprint in science, culture, history, literature and technology," says Harlow, whose sparkling exhibit runs through April. "They're just magic."
Did You Know?
Smithsonian's National Museum Of Natural History