"Will I ever smile again?" Carolyn Creasman asked her doctor. Her husband was recovering from surgery that nearly killed him. A bitter strike was tearing apart the mining company where she worked as a secretary. Her nerves felt so shattered she could barelv crawl out of bed.

What brought back Carolyn Creasman's smile was a dull gray metal called lithium. It is the lightest solid element on earth, as cheap as beer and simpler than air. Yet the designers of the Space Shuttle clamor for the stuff, and so do a million swimming-pool owners, the makers of the Titleist golf ball, the international fruit industry, and discriminating grease consumers everywhere.

Lithium's frail figure — just three electrons — makes it one of nature's nimblest acrobats, able to wriggle in and out of the narrowest molecular crevices. It is also an inordinately attractive little atom, apt to bond with nearly anything.

Myriad Possibilities

The result: stunning transformations wherever lithium goes. Pour lithium in. molten glass and it comes out lighter and stronger. Add lithium to concrete and it hardens faster. Lithium kills algae, scrubs carbon dioxide from the air in spaceships and puts the juice into wristwatch batteries.

Also, every day, millions of people around the world swallow it in various dosages. It keeps the from binges of promiscuity, psychotic rages, out-of-control spending and suicide. Doctors aren't entirely sure why. But for 25 years they have been gratefully prescribing lithium compounds to patients with manic-depression. It is one of the most improbable therapies in all of medicine, a chip of salt that treats mental illness.

It certainly seemed improbable to Carolyn Creasman. For years she had been mystified by her wild mood swings. "I could whip the world. Everything was wonderful. I was happy. Laughing, giggling, just on top of the world. That would last a few days. and then I would go into my lows."

As a joke, her father presented her with a two-faced doll and told her, "You have a happy face and a sad face." Ms. Creasman believed she simply had a quirky personality.

Before and After

At her deepest low ever, when her husband had his brush with death 15 years ago, she dragged herself to a doctor. He concluded she was manic-depressive and prescribed lithium. Today, at 61, she takes out a pen and neatly draws two diagrams to depict her life before and after: a jagged fever chart, and a straight line. "I don't have the highs, I don't have the lows. and I don't miss them," she says.

As it happened, the solution had been literally at her doorstep for years. Ms. Creasman works for the international conglomerate FMC Corp., which pulls the lion's share of the world's supply of lithium from a giant open-pit mine just down the road from her desk.

Outside her office, long trucks dump mounds of ground ore into an enormous rotating kiln. It spits out glowing molten rocks, onto a web of noisy assembly lines that turn them into lithium ingots and powdered lithium compounds. Each morning, Ms. Creasman had walked past barrels of lithium carbonate and had seen trucks cart them away for delivery to drug companies. "It never dawned on me," she says.

Lithium, element No. 3 on the periodic table, was discovered in a Swedish iron mine in 1817 and quickly became the object of health claims. The British physician Sir A. B. Garrod advocated rubbing lithium and rose water onto gouty joints. Merchants raced to hawk lithium preparations as nostrums for dyspepsia and gallstones.

One, C. L. Grigg of St. Louis, came up with a fruity concoction he named "Bib-Label Lithiated Lemon-Lime Soda." A doctor's testimonial promised "an abundance of energy, enthusiasm, a clear complexion, lustrous hair, and shining eyes."

Mr. Grigg later came up with a punchier slogan-"You Like It, It Likes You"-and a new name: 7Up. (His successors took the lithium out of the soft drink 50 years ago.)

Elsewhere in the U.S., travelers flocked to "lithia water" spas in Waukesha, Wis., and Lithia Springs, Ga., where Lithia Springs Mineral Water ("a bit of history in every, drop") is still sold to devoted self-healers.

"It keeps my nerves steady. And when I quit drinking alcohol, it was the only thing that kept me sane," says Matthew White, a lanky, young yardworker from nearby Smyrna. He says he drinks a gallon of Lithia Springs water a day, and also gives it to his dog, Sonnv.

Start of an Industry

Lithium became a big business alter World War II, when the U.S. government discreetly made it known that it needed large quantities of the mineral for a secret project. Mining entrepreneurs swooped into central North Carolina, site of one of the world's largest veins of a lithium-rich ore called spodumene.

Soon a start-up company called Lithium Corp. of America was supplying a vital ingredient in the fusion-reaction of hydrogen bombs. But that fat contract expired in 1960, leaving the company with a huge oversupply and a need for new markets.

They sprouted everywhere. Lithium hydroxide made grease greasier. DuPont Co. used lithium to create Surlyn, the "cut-proof" golf-ball cover. Lithium carbonate became the secret of frit, the super-flexible glass coating that keeps stove-tops from cracking from the heat.

The most unexpected new market arose in Australia in the 1940s, where a psychiatrist named John Cade was working alone in the pantry of the Bundoora Repatriation Hospital on an extremely odd experiment.

He had injected the urine of manic patients into guinea pigs and found it was surprisingly toxic. Searching for the poisonous ingredient — and a possible clue to the biological causes of mania — he gave the guinea pigs uric acid.

The result took him aback: The normally jittery. animals suddenly became lethargic. Dr. Cade turned them on their backs, and instead of scurrying away, they lay still and gazed serenely, back at him.

It happened that Dr. Cade was using the most soluble form of uric acid, lithium urate. He hadn't previously been interested in lithium, but now he impulsively swallowed some himself. Then he administered lithium to 10 manic patients and watched thunderstruck, as their raging moods subsided.

It took decades for doctors to master the delicate weapon Dr. Cade unearthed. Patients must have their blood lithium levels checked several times a year. A slightly high dose can cause weight gain, mental sluggishness and poor concentration. A very high dose can be fatal. Some patients struggle with the side effects and miss the exhilarating highs.

Nothing Better

Nevertheless, modern science has yet to come up with a better first-line treatment for manic depression. The sleek new generation of popular antidepressants, such as Prozac, can work wonders for simple depression, but not mania.

At FMC, which bought Lithium Corp. in 1985, miners and salesmen joke about their unlikely role in regulating the world's mental stability.

"Everyone feels great here all the time. It must be osmosis," says James Holman, who runs the FMC lithium mine. For a recent executive meeting, an FMC wag prepared a mock TV ad featuring stressed out office workers hitting the bar for a refreshing round of "Lith Beer." Soon the happy 'drinkers are slumped in their chairs with vacant stares and goofy grins.

For Carolyn Creasman, the jokes all have an element of truth. "I feel so grateful to my company, she says. "We made the lithium, and it was a miracle drug for me. For the first time in my life, I understood my whole life."