Kenneth Chang
New York Times

In oil, scientists have struck diamond.

Researchers at ChevronTexaco in Richmond, Calif., have discovered tiny diamond fragments of a wide variety of shapes and sizes within crude oil from the Gulf of Mexico.

Nothing that could be used for a ring or a necklace, though. Even the largest fragment is far too small to be seen -- less than a billionth of a billionth of a carat.

But the infinitesimal size could be just what scientists want: potential building blocks for the construction of molecular-scale machinery.

"A good analogy for these are Legos," said one of the researchers, Dr. Jeremy E. Dahl, an organic geochemist at ChevronTexaco. "It's a brand new set of materials that no one has ever looked at."

The diamond fragments, which form naturally in petroleum and natural gas, could also find use in electronics or as novel drugs.

Dr. Dahl, along with his colleagues Dr. Shenggao Liu and Dr. Robert M. K. Carlson, will report their findings in a future issue of the journal Science.

"It's just magnificent work," said Dr. Alan P. Marchand, an organic chemist at the University of North Texas who has written an accompanying commentary for Science. "What they've done is alerted the community that these things exist, and you can get your hands on them."

The strength and hardness of diamonds come from strong chemical bonds between carbon atoms.

Each carbon atom in a diamond is connected to four neighboring carbons, the bonds splayed out in a tetrahedral configuration, forming a strong, rigid three-dimensional crystal lattice.

One can imagine chipping tiny fragments, or diamondoids, off the diamond crystal. The smallest possible fragment, containing 10 carbon atoms, was first discovered in petroleum in 1933.

With an amino group attached, the 10-carbon diamondoid has served as the drug adamantine to fight the flu virus and, more recently, to reduce shaking from Parkinson's disease.

In subsequent decades, scientists found a few larger variants, with 14, 18, and 22 carbon atoms. They also tried to synthesize the larger diamondoids from scratch, with only slight success.

"It was a very difficult and low-yielding synthesis, and they basically gave up," Dr. Carlson said.

The ChevronTexaco discovery may revive interest. The researchers' work started because of practical oil-drilling concerns. Diamondoids can clump into hard, diamondlike deposits that clog pipes. Dr. Carlson said that a decade ago he found signs of diamondoids larger than previously seen, but did not explore them in detail. The recent rise of nanotechnology -- devices on the scale of a nanometer, a billionth of a meter -- led him and his colleagues to take a closer look.

Diamondoids survive high heat that destroys other molecules. Roasting gallons of petroleum at 850 degrees Fahrenheit breaks down the other compounds in the oil, producing teaspoons of the larger diamondoids.

The researchers sorted the diamondoids by shape and size, finding dozens of new varieties with up to 39 carbon atoms. Some are shaped in long rods. Others twist around like a corkscrew. All are less than one 10-millionth of an inch long.

Nanotechnology researchers have for years imagined what they might be able to make with diamondoids, but until now they have been able to explore those ideas only with computer simulations.

"It creates quite an opportunity for someone thinking how to construct something on molecular scale," Dr. Carlson said. "They're about as rigid as you can get."

ChevronTexaco announced yesterday that it would sell small amounts of diamondoids commercially.

The ChevronTexaco scientists said it was conceivable that the new diamondoids could be chemically modified to make new drugs or tiny electronic components.

It may even be possible to string diamondoids together into a sort of a nanodiamond necklace. The strings of diamondoids could perhaps then be used to add some diamondlike properties to other fibers.